Well, assuming the E-box is OK and AC/heater has no damage, I can't see 20k in repairs here. Main engine harness is about $400, and depending what was removed before the fire, I'd say 3-5 K in parts. I don't think engine has any damage, it needs paint job on the intake manifold, and would have to come out for proper repair. The big question is E-box, AC/heater unit, and the fuse box. Anyway, I've sent question to the seller to email detailed pictures of the underhood area and parts in the trunk.
I believe, if the price wouldn't go much higher, it may make sence for big DIY project.