www.drivetrain.com has rebuild kits for our trannies that cost about 80 bucks or so.
there are also vendors on ebay that sell basic rebuild kits.
better call and ask what those kits include. typically the basic kit should be a few gaskets, seals, and all major bearings (hopefully including the main input shaft bearing).
for future reference our transmission is a FS5W71C nissan tranny