the 1.8t is a 20v. that being said, the 2003 gli was not a 1.8, it was a vr6, 4 valve per cylinder, 24v. you have to look into a few things when swapping out ecu's. you have immobilizers, which can be defeated. you have engine codes (AWW, AWP, AWD, AZG, AVH, and there are others) that have to match up, and other small things. it's not a plug and play deal at all.
"chipping" is an old term which we still use for "flashing" our ecu's. Flashing is typically done in 15 mins- 1 hr. The term "chipping" hails from the tuners actually opening up the ecu, and soldering a bridge between, one or more circuits and literally inserting a chip in some cases. The only place i think that still does that, and it's only on the high end tunes, is unitronic. Somebody correct me if i am wrong on that and they have moved completely to flashing.
long answer for info you were't looking for, sorry!