My guess is its not worth it. Get a brand and model # and contact the manufacturer for the rebuild kit cost.
On almost all screws under 150HP, a "kit" is usually a new compressor head at 75% of the cost of an entire new unit, without the warranty. When they go, the screws usually gouge the housing, rendering it junk. Since they run oil circulation through the air and all moving parts, everything else inside also becomes junk at that instant when chunks are floating through.
Also, don't ever buy a compressor where they say they are "upgrading to a larger unit". That's code for the the thing has run non-stop at hellish temperatures.
Last year I got a new 10HP/40cfm Quincy screw/dryer 120 gal combo (made in Italy) installed for the shop at work. It was under $10k delivered with a 2 yr complete warranty. The shop air has never been dryer, and I rarely desire more volume. It is super quiet and has needed nothing in the first 4k hrs. It's really not terribly expensive to get into the screw world if you truly need that much air. You don't want to be short tripping a screw. They need to run minimum 20-30 minutes every time they start to drive the condensate water out of the oil.
Greyson