2003 FX45 stereo installation question

[chemao]

I'd like to swap out all the speakers in my FX45. I'd like to avoid having to do a custom install or any fabrication. I'd just like to drop them in. Has anyone done this and if so:

What size speakers does it take and what recommendations do you have?

Does the factory stereo have any RCA output for a sub amp?

Can the factory system have an amp? Where? Can you swap it out?

I hope you guys can help, this is the first step in my build.

justin