Importing glider kits into U.S.

A friend of mine in Russia works for a small aircraft manufacturer (gliders and motogliders) http://glider.ru/
They are trying to start exporting their gliders into the US again as kits. The previous owners sold over a 100 motogliders to the US before the company bankrupted in 2005.
So now they are trying to figure out all the paperwork needed.
They are looking to export either a ready to fly aircraft or as a kit (90%/70%/49%).

So if anyone can point me in the right direction of where to find relevant FAA documentation I would appreciate it.

I would start by talking to your local Flight Standards District Office. They should be able to tell you what is involved and who else you would need to talk to. One of the local guys here is trying to do something similar....some weird Chinese aerobatic aircraft thing.