Well, the trailer is worth 300, and the motor should fetch $300 even if you sell it for parts.
Expected costs:
transom 200-400
floor 400-1000
seats 200-1000
wiring, side panels, hardware, and misc. 300-1500
motor 100-1000
Then there are things like electronics, stereo, steer and control cables, controls, fuel tank, lights, tires. side guides, etc, which are unknowns that could easily cost up to $3000
So you are looking at spending between $1200 and $7000 to fix her up, depending on materials used and how nice of a finished product you want.
Been there done that, did one cheap, and did one all out. I will never get my money out of it, but plan on keeping it till I can't boat any more.
So, before you dive in and spend 200 hours working on it, divide if you might be better off buying a water ready rig.