Hey, sounds likeit'll be a cool trip. I haven't kept up with the world of backpacks lately, so I can't currently suggest a certain model/brand. However, I can give you some general suggestions (I hope you find this info useful):
-try on the backpack before you buy it, unless you are well-experienced. Backpacks are like boots - no two fit alike. Every person has a different frame and, therefore, needs a different size and shape of bag. A ten-day trip is a long one, if your pack is miserable to carry.
-if you can get into a store to try out packs, take along the gear you will want to have with you. This way, you will know the size and dimensions that you need. Also, you will be able to compare fit while holding your gear.
-to find the length of your back (and, corresponsingly, the size of pack you need), measure in a straight line along your spine, from the large, bony vertebra at the base of your neck (I think that is #7) to the point inbetween your upper-most hip bone (also called the iliac crest). Backpack lengths are sized to accomodate that section of your back. Some packs are very adjustable, some are very specific.
-the pack weight should ride more on the upphips than on the shoulders. However, this can be adjusted for certain types of hiking. The shoulder straps should not pinch or rub you raw.
-when choosing a backpack, the most important feature is how it fits on you. Secondly is price and features. An internal frame pack could very well be the way to go, but don't wolly rule out external frames; in my experience, I often find an external frame pack to be more comfortable and convient.
Good luck and, if I come across any more specific info, I'll pass it on. Hopefully, the others will be able to chime in.
