A/C evaporator replacement instructions needed

That is basically the same truck as the Canyon here in the US so those procedures should work. The biggest issue will be that the AC system uses R1234YF and unless you are certified it cannot be bought and is unbelievably expensive as well as requiring specific tools to work with it.
Being you are around the 60,000 mark I would probably see if Isuzu would cover it under warranty as my first step. Talk to the dealer first then corporate if they balk at the idea. A two year old truck shouldn't be leaking at this point.

As for changing it, The dash has to be removed to get to the HVAC case, Cooling and AC have to be drained and recovered, then it is removed from the truck and split to get to the heater and AC cores. Then you reverse the process and recharge the system.
Is this is a RHD vehicle?

Well that is BS. If it isn't listed as a service item then you don't touch it and just how do you "clean" the evap core when it is buried in the dash? I would move up the food chain and call corporate about it. Be sure to have the stealerships name and address handy.

Manila (632) 757-6070 Laguna (049) 541-0224