On most A/C systems the evaporator is a separate and serviceable / replaceable part. [My 2001 Durango needed one.] Won't be a cheap part though, not sure if they can be re-brazed, etc. for repair.

Many Japanese imports had the A/C system added in the US at the port of entry to minimize duty costs - not sure about T100s but this may mean that it was designed to be a bit easier to get to and service.

Jeff
96 T100 SR5 4WD Ext Cab, Warn Hubs, HD torsion bars, Bilsteins, Camper Shell, TJM bar, factory 31 x 10.5's, Powertrax No-slip rear, Recaro driver's bucket