Can this be done and if so what needs to be changed or is it a straight swap? Please let me know.
It's not a straight swap, and not much doesn't need modifying(actually, everything does). Don't bother.
I concur with word03. A quick look at any of the Apple take aparts for them will show you just how different they are.
BTW the slotloader is larger than the original tray loader, so it wouldn't be a straight fit no matter what.
You are better off upgrading your CD to a slot-loading 20x CD-RW and then popping in a CPU upgrade. The mobo is what is your real stopping point here (unless you were to mount it vertically, but you would have to replace the CRT with an LCD and reroute all of your i/o ports to someplace that you could actually use them and have to come up with some way to secure it all after gutting all of the current internal bracing and such...).
I would upgrade the CD, the CPU and the hard drive and call it done...