With 34 hours on a 30 year old machine, I would guess you will need at minimum final stage valves, possibly all the valves and fresh oil. Units that don't run rust a lot.
Plus a motor or VFD, you will have three grand in making it a good running machine.
It being 5hp makes it desirable for the home user, but lacking auto drains and proper filtration drops it a lot. I would guess it is worth around $3-3500 after you have gone through everything.
If you paid about a grand, you got a good deal. Those are great machines and very much worth fixing up for your use. If you paid $2500, you should have asked more questions before you bought it.