$600 for a full years rego is about right for a larger car half that is approx $350
if you only have 6 months rego left and you hand in the plates you will only get $250~ back coz of admin fees etc etc
As hermit said you will need to get a temp moving permit for $14.50 before u can drive it to another workshop to get it repaired/engine/gearbox change. then an inspection fee of $56.50 and if you fail you'd have to pay a re-inspection fee of $30 something. As long as the car has compliance plate, and you have previous rego or transfer papers you will be fine.
I havent had any inspectors ask for a list of parts repaired and ive been to pits around 8 times (different cars different issues) i go to the welshpool pits.
Down side is you will save $180 if all goes smoothly but your going to have to get to pits very very early like 5am to beat the crowd coz when they open at 8 theres lke 30-40 people infront of you and if you allow 20-30 mins each thats easily a few hours wait
gawd thats a long type, hope it helps