Hi Jenny,
you can watch keyhole RP and Da Vinci (robotic) RP videos on Youtube - easy to find via Google. However, you don't know yet whether the op would be keyhole or open so don't watch so many things that you terrify yourself and then discover that wasn't what he would have anyway!
Peter has linked you to his description of keyhole RP. My husband chose open RP - the two ops are quite different in terms of what actually happens. Main differences:
Open RP - shorter time under general anaesthetic, no blowing the belly up with gas, longer time in hospital (often 5 days), longer time off work (up to 12 weeks depending on the nature of the work), much bigger scar, more risk of blood loss, no clips to get left behind.
Keyhole or robotic RP - longer time under general anaesthetic, operation is done with person tipped head down (so not suitable for some people with heart conditions), belly is filled with gas to make room for the operation, much shorter time in hospital, often (but not always) back to work sooner (average 6 - 8 weeks),, less risk of blood transfusion, more risk of clip migration
I think 3/4 hours would be pretty good for any RP - my husband was under for about 6 hours I think but that was because they found they had to redesign his bladder while they were in there.