That sound about right for the engine & tranny (the $1500) if they are good.
Keep in mind that there are other parts required for the 5 speed conversion, seen in the following link:
http://www.toyota-supra.info/forums/...95&postcount=2
Seems like so many want to change things around when they first get a car.
I would wait and see if things are OK before making a revolution with it.
(Just how I think. I would get to know it first.)
Anyways, it sounds as if you got a good deal. Post some pics.