I, too, have never played. My little cousin has/had it, though. It looked pretty easy... The zombies were really slow...then again, there were TONS of them, so I guess that's where the difficulty comes in.
Faaantastic! I love this, haven't seen this crossover before. I could see Trixie getting caught up with zombies, ha. Dead Rising's game-play is pretty addictive, if you haven't played it yet, you should.