explorer help in australia

Hi guys, needs some help again, The overdrive light on my 98 explorer is flashing from reading some of the responses from the group i took it to a transmission specialist cos it is making some funky noises but still drives ok, since the light has started to flash 1 day ago it changes gears a little bit clunky (automatic) the tranny specialist rang for a change over quote and was told $7000 from ford australia or $5000 for a recod one change over, he said that internals are non existant here, how about over there is there any one who makes aftermarket internals for the gear box as i plan to pull it out and hopefully supply him with the parts to fix it, as $7000 australian dollars is pretty much 3/4 of the cars value cheers guys.