SSgirl,
I have some advice to offer. I am putting together an AT setup this off season by trying to take advantage of summer sales and such. I have only bought skis so far, waiting for mid August tent sales to look for boots. Here is what I have learned from looking into it for a year or two.
To try it out, go to Bolton Valley in VT, 10 miles south of Burlington and a bit North of your usual ski destinations. They have a medium sized down hill area, a reasonable resort development with lodging, and a huge X-cross country / back country center with a huge trail network. They have a "intro to AT" class on Saturday mornings and they rent all the AT gear and cross country gear. On Sunday mornings they offer a guided tour of their back country network and choose terrain based on who's in the group that day. The prices are very reasonable and the gear is very good. I stopped there one day to scope it out and was impressed and plan to go back and do some skiing there next season. You can stay on easy xcountry trails, do the more advanced back country trails, set out on a long trail with a car waiting at a destination, or skin up the downhill area. Your choice.
I have not tried anything in the Whites, but anything by the AMC is usually very good.
I have actually never done AT, so maybe I am speaking out of turn, but my good ski buddy has been through 2 sets of gear already and I am learning from his mistakes. I am a ski race coach, so I am gear knowledgeable. I also have xcountry gear and have been doing it for years. Skinning is pretty similar to xcountry in terms of stride, fairly different in terms of traction and gear.
Definitely rent the gear to see if you will like it. I love xcountry and alpine, so I already know I will enjoy AT. (if I am in shape, that is) I don't mind working my way into shape and know how to start out small and work my way up.
Why I want to do it?? Several reasons, I have been deep into Bracket Basin at Sugarloaf and had to hike in my race boots with my skis on my shoulder. I didn't find this fun for very long and skinning would have been much better. So sidecountry will be on my agenda, depending on the area. I don't plan on skinning up the ski slopes if the lifts are running, I am too lazy for that. I like your idea of closed mtn skinning for some exercise and fun. I also will work my way up to a Tuckerman trip or Gulf of slides. I have hiked my down hill gear up to Tucks about half a dozen times. My AT buddy says skinning up will be way easier. I hope he is right. I can also see some night skinning for kicks after a few too many when staying in a slope side condo.
Well, you know how heavy down hill gear is and especially hiking up in ski boots with skis on your shoulder. Xcountry gear is the way to go for the up, my stuff is as light as sneakers, but it sucks on the way down. AT gives you the best of both worlds with some weight penalty, which you choose how heavy or light you want to go. Light approaches xcountry weight, but doesn't ski great on the way down. Some AT gear is even heavier than Alpine, and is really Alpine gear that you can lift your heel. This is called Frame bindings and works well for side country and short distances. I direct you to Blister Reviews for very good articles describing the different AT gear classes. There is also Tele and Xcountry bushwacking gear. Too much info for me.
What made sense for me is a light ski (actually towards the heavy end of AT skis) that I can use 50/50. I have a opening in my downhill quiver for a 110 ski, so I bought a 108cm Blizzard Zero G ski. It weighs 1700 grams. Downhill skis weigh 2200 grams and really lite AT skis weigh 1200 grams. My xcountry skis weigh about 200 grams. I paid $550 for the skis, new. They are one of the best downhill skiing AT skis.
Next is bindings. For me there is only one, the new Shift by Salomon. It attaches to your boot the same as a downhill binding for the down, and for the up it has pins for your toe attachment and your heel is free. This is a combo AT/downhill binding. It weighs 800 grams. Light AT bindings weigh 400 grams and frame bindings weigh 1400 grams. The light bindings don't hold you as rigid to the ski as downhill bindings, the shift will hold as well as a downhill binding. The light AT and Shifts cost around $500. Frames can be less.
So if you haven't figured it out, weight is every thing when going up hill. So now we come to boots. You need a walk mode, which lets you go back a lot more, not front ways any more. You loosen your top buckles for getting more front range of motion. Boots come in a range of weights. A downhill boot with a walk mode works if you get pin inserts for the toes. With frame bindings you don't need the pins, the pivot is in the downhill style toe. This works for your down hill boot too, so you can have only one boot. It will be at the very heavy end of the scale, but ski downhill very well. Really light AT boots suck at the down hill, not enough support to lean on them much. Almost like xcountry boots. I am shooting for the lightest boot that has good downhill skiing performance. It will weigh around 1500 grams. My Lange race boots weight probably 2500 grams. BTW, 450 grams equals 1 pound for reference. I hope to find boots at a summer sale for around $400-500.
So I will be into it for around $1500 and then $150 for the skins. Skins are custom for the ski you have. I think they come in different widths and they cut them to length for your ski length. Mohair seems to be the best. Blister reviewed skins and you can read what they have to say.
Good luck and I hope my brain dump helps. It took a while to type at least.