I asked around and it was quickly obvious that it wasn't worth getting it
repaired, may as well buy another used engine or even a new one.

But what about doing it myself? Good idea or bad?
I am reasonably mechanically inclined, know enough to use a torque wrench,
etc.
Any suggestions where to find parts? (at least piston, rings, water pump)

Will most certainly need a new piston and ring pack.
Cylinder probably needs to be bored and honed.
Wrist pin may also be baked. Conrod too?
Will bottom end bearings be typically more resilient and possibly ok?
Will need water pump, thats what caused problem in the first place.

Although old in calendar years, this engine has seen very little use, so I
am reluctant to just toss it away.

What do you think?

Sniffinvinyl