Overhaul kit ~$200-400. Most DIYers send the OD section out and do the main case at home. Watch for solenoid and 3-4 clutch wear.
The AW4 rebuild is doable in a home shop but not trivial. The standard advice: pay a trans shop to do the overdrive section (requires specialty spring compressor) and do the main case yourself.
Gaskets and seals (front pump seal, rear output seal, valve body separator plate gasket)
Bushings (front pump, planetary)
Bands (intermediate, OD)
Filter and pan gasket
What usually needs replacing at high mileage:
Front pump bushing (groove visible)
3-4 clutch pack (charred friction material)
Solenoid pack inside valve body (electrical drift)
TCC lockup clutch in converter (a new converter is cheaper than rebuilding the OEM)
Tooling: standard mechanics hand tools, a snap-ring tool set, a press for the OD section (or send it out), a flat clean workbench. The shop manual or the Toyota A340 manual (they're 95% the same internals) is mandatory.
Timeline: a competent DIYer takes a long weekend. A pro shop turns the job in 2-3 days for $1500-2500 all in.
Cost reference:
Reman trans (Jasper, Monster): $1800-2800 + core + shipping
DIY with kit and new converter: $500-700 in parts, plus your labor
Junkyard pull AW4 from a 97-01 XJ: $300-600, totally a gamble
Written and maintained by an AZ wheeler and driveway wrencher. Always cross-reference your factory service manual — modifications affect vehicle safety and warranty. Work at your own risk.