Yes, cylinder #4 is the cylinder closest to the firewall on the pasenger side. Yes, you can swap the misfiring cylinder's COP with one from another cylinder; if the COP's bad, the error should follow it.
You'll definitely want to check the plug wells for oil, but the only way to really check is visual inspection. For those cylinders you can't see directly, you can stick a long cotton swab (like the kind the doctor uses to check for strep throat) down in the well. There shouldn't be any oil in there, so if it comes out with oil, you know the valve cover seals need to be replaced. It's possible that it's just a bad coil (that does happen), but the normal cause is damage from oil contamination, so I'd definitely be pulling COPs and checking for oil...