Repairs for most people come in 3 varieties:
1. Standard Periodic Maintenance
This is not only the daily check the fluids and lines, but also the every 400 hrs / 1200 hrs filter and fluid changes, and adjustments to things that loosen up, get dinged, stretch, etc.
2. Fix or replace a broken part.
Could be as simple as a light, or as bad as a clutch disk replacement. Still, it's only a single part.
3. Overhaul a system or assembly
Think of rebuilding an engine, or a transmission. Not just a simple part replacement, but making that system as good as new.
There's a 4th level of maintenance that people rarely do, other than collectors, hobbyists, or fanatical mechanics, and that's what military types would refer to as a depot-level re-manufacturing. An overhaul of that nature is equivalent to overhauling every system on the vehicle or equipment, not just the system you've been having problems with. You just about completely disassemble the tractor, spec all the parts, replace the ones that don't pass muster, and then reassemble the entire tractor. What you have then, is the same tractor, in just about factory new condition.
That kind of an overhaul requires either a complete motor vehicle garage/machine shop to do it in; or a lot of barn floor space, time, hoisting equipment, time, tools and did I mention time?
The benefit of all that work, and money is you have a tractor that shouldn't require anything more than the periodic maintenance that a new tractor requires. And should be cheaper in the long run. But that mostly depends on what your time is worth.