I've got over 230K on my 95 SR, and the majority of the drivetrain components are still original. I pulled the cylinder heads at 130K to replace the valve stem seals but the bottom end of the engine has never been touched. The transmission has had nothing done to it but fluid changes. I've switched to 4.90 gears in the axles but they were both still working fine with no noises prior to that. overall, the significant components tend to be pretty stout if they are maintained - the maintenance that yours has had sounds like a major bonus, especially if it was by a tech at a Mitsu dealership. Having been a service advisor at a Nissan dealership, my experience has been that dealership techs will usually use factory parts, are very familiar with the common problem areas on the vehicle, and tend to do the repairs correctly (of course, that may vary by the individual technician, but if he worked there for 10 years he probably wasn't a hack). This means that issues like the lower intake plenum will have been taken care of, and maintenance will have been done with correct fluids and parts.

The types of issues my Montero tends to have are typical for vehicles with higher mileage - window regulators, wheel bearings, rubber mounts and bushings. Living in dry AZ is hard on rubber parts, and wheeling it fairly hard on 35" tires has no doubt accelerated the wear on the suspension and steering components, but I generally keep it pretty well maintained and it doesn't leak anything in my driveway.