Hi again Siljo,
I am also a low-houred pilot (500 TT) with a Airbus A320 Type Rating. Consequantly, I am now used to the performance of a jet, but will undoubtedly go and fly the 737 prior to go to the sim screening if successful on the first part.
I think that to be accustomed to that kind of aircraft, at least 3 hours should be performed, preferably split into two sessions. It is for sure even better if you may fly a bit more, but by far not a guaranty of your sucess. Ask the instructor to behave the same way that the one at the sim screening and carry out different approaches.
Brush up your IFR procedures and do your best on the D Day. I will try to do the same !
Anyway, the sim assessment will obviously remain a very hard time according to our friends' testimonies.
Keep up the good work.
Cheers