There's nothing written about a weight limit for first officers, for captains it depends on which fleet you are applying to. If there is an unwritten rule I honestly couldn't tell you what it might be.

As far as sim prep, anyone with the experience to apply should know how to do a V1 cut and raw data ILS, I can't imagine it being worth the money to pay for prep course. If you have flown airbus, brush up on using the flight path vector, or "bird". Non type rated, you have the instruments in front of you, fly the numbers.