the torque converter is under no load at any angle when the transmission is bolted to the engine, once all the bell housing bolts are in place and tightened, the Torque converter and engine are rotated so the drive plate holes line up with the converter holes and the first bolts are put in, once the first are installed, you just spin the engine and install all the bolts. Just like you take them out. I doubt any mechanic can be stupid enough to try to not do that. The seal can also leak if the mechanics dont use any sort of assembly lube in the seal spring cavity, which can dislodge the spring and cause leak.
anyway - I know whats available in Pakistan and whats not at the dealership, some are so complete jackasses that they buggered up a CF3 Honda accord to the extent of dashboard removal and what not while the only problem was their chief mechanic reversed the wiring of the TPS and MAP sensor. THAT WAS THE CHIEF MECHANIC!!!! still the numbskull couldnt see bad tps value in the test log.
this same dealership screwed up the same car's EPS. a plain reset and small troubleshooting (very simple with battery powered dollar marker case test leads found the fault)
btw - for alien car parts like the 3SFE - yes you have to wait as its not a local car engine, however the electronic ignition coil for the toy distributor is available. Just get the parts cartoon to look up the part no. and ask him to show the inventory available in Pakistan. Usually they have a ton of the stuff but are just too lazy to look it up because they are more interested in talking to insurance agents for big money as saith saab of the dealership would fire him if not.
If your dealership is installing used parts, get them to write it on the work order and then post it to Toyota Indus Motors asking an explanation of this. It is not allowed and infact can land the dealer in a mountain of ***** and pain. I have dealt with them and usually would steer their priorities straight, I think the factor of me being their "go to person" for weird strange problems - like an AE100 corolla auto which refused to shift out of 1st gear (auto) - solution - speed governer stuck with garbage.