You can get all your answers here:
http://chinookrvforum.com
There is a Glaciar for sale in the classifieds for $65k. I never looked into Glaciars but have its little brother (Concourse). Assuming $65k is good number for 2wd, it would min. cost $20 - $25K to have professional upgrade to 4wd, plus another $2.5k - $3k to have winch/bumper installed, so your really not far off, plus new bigger AT tires (7 of them). However, 4wd drive Glaciers may be tough sell due to small pool of potential buyers with $100k to drop on it.
I think 4x4 glaciars are pretty rare so trying to find another may take time, lots of it. This looks like really nice rig and with 4x4 it may command premium. I would be worried about the side slideout while using 4wd capabilities.
If you are serious about this check out the Privan Tiger Bengal (
http://www.tigervehicles.com), for $80- $90k you can get 2012/13 built on Ford "F" series truck that has advantages over "E" series vans. However, if you don't need permanent bed I think Glacier interior nicer than Provan's.