If you go under the gliderpedia link, there is a housing link for all the recommendations and the size being 32x20x30. I personally have a custom cage I just recently built if you would like to look at it on my photos to get some ideas.
You are right though, size is very important because they need lots of room to run, jump, glide, etc. A wire cage is great but be sure it is coated wire at least 1/2" spacing or less. Galvanized wire can cause urinary tract infections.
Good luck with your friend and helping her get set up. Feel free to ask anything else and if I can't help, there are many people here that are always willing to offer advise