yes to all your questions. It's versatile enough to do any of your queries, though you'll need to get familiar with the engine before you start doing anything fancy.

Just pointing out some pros and cons with each engine, as I am trying to work out which engine to do my project in. UDK: Pros: Good Hightmapping tool... the PAS one has lines running through it, and gets wierd when lightmapped. The UDK heightmapper is great. UDK has a version of speedtree, which mea...

1 question... would the player be zombies, or kill zombies?

to Johnno56:
The thing you really need is something that can light all textures exactly the same, no matter where the textures are (I think it's called a 'hemilight' but im not sure). I don't know whether PAS has hemilighting (we'll go with it) capabilities, you should probably find out.