What kind of display case? A large one to hold many models, kinda like what a retail store places more valuable items in? Or a box like case to hold just one model?
I've been down this road and can tell you it can get expensive, even building your own. I've tried glass and plexiglass, both ended up looking like crap.
For me the most difficult part was the cutting of the glass or plexi. Assembly is a pain but doable with time and patience. I just couldn't get the hang of cutting. Those darn videos made it look so easy!