which one do you want to know about? The 280zx's were made from 79-83. YOu may be thinking about a 280z. Those can cost a ton or very little, depends on what area, what condition, etc. I paid $1200 for both my 240's combined because the guy knew I really liked them and he HAD to get rid of them fast. Engines, for a good used one without rebuilding it is anywheres from $350-600, and about $1200and up for a rebuilt one. Just have to look around in your area.
Hope this helps,
I would get the blue book value. and when u find a car look it up. If they are asking to much for it tell them look it up some time they will go down. My 280zxt 1983 was around 1,200 but I got it at 1,000. So look around and use the book hehe.