I've lost my manual so can anyone advise on these 3 points?
1. is the oil pump accessed by taking off the pan?
2. Also could a clogged oil filter cause the check engine light to come on?
3. Is there a way to test the pressure switch?
Thanks!

1. not sure where the oil pump is located on the 2.4L, but you can check the FSM in the link below to see where it's located.

http://www.ncttora.com/fsm/index.html

2. there are a multitude of examples that would cause a CEL to come on from a loose gas cap to a cylinder misfire. Go have your CEL checked at an AutoZone (they do it for free) and post the code in this thread. That way, we can see what the code is and give you a better grasp of what needs to be done.

3. are you talking about the oil pressure switch or something else?