I put a new glove box deal in my truck last year ... I removed the glovebox door and inserted the new liner in from the front -- had to collapse it a bit to push it in past the opening, then it expanded back (once it was past the opening) ... then I pushed it forward into position and attached it properly.
You can see some pics of the install here (scroll all the way down to bottom of page):
New Glove Box Install
54 Chevy Pickup