The conversion is really easy.
AGU is prop the easiest conversion it has the cable throttle.
An it is the cheapest to buy out of the 1.8t's.
If you did buy one, whilst the engine is out I would rip all the PCV system out and replace with catch can.
Drain the oil, take sump off and clean/replace the pick up pipe.
Full service.
Replace timing belt along with water pump etc
Maybe port the standard exhuast mani and put back on (Better flow before remap)
You will not have to touch the engine for a VERY long time then that way.
The last thing you want to do is fit the engine an one of the above failing on you mate.