Yep 5k is a bargain, you could strip it and sell it for more easily. If its been sat outside for some time it will take a large amount of cash to get it on the road again, but again at 5k I wouldn't worry about that at all.
Manual swap wise I'd say you're looking at 10k+ for a v160 swap with big diff, pedals, clocks etc. if you go w58 (n/a box) and small diff then maybe half that.
Gte engines are roughly 4k last time I looked
I suppose the real costs mount up if you get a competent mechanic to do the work, if you're handy with a spanner you'll save a fortune in labour.
Either way get it bought regardless before someone else who see this post gets their grubby mits on it and sells it for 15k after a little service.
Good luck!