first things first, I use the wichu sprite editor to edit my sprites. it's much easier and more user-friendly, although you might still need to use UNLZ for more in-depth things (such as the custom type sprites)
That program can be downloaded here:
http://www.pokecommunity.com/showthread.php?t=196143As for your questions...
1. DoesntKnowHowToPlay made a patch for fire red/emerald that adds in the physical-special split, which can be downloaded from here:
http://www.pokecommunity.com/showpost.php?p=7465618&postcount=163. no permission from DoesntKnowHowToPlay is nessicary, but you do need to give him credit.
Something to note, is that
you will need to edit every move to be physical/special/status yourself, which can be done using an attack editing program, such as the attack editor pro. not linking to that since there's a more in-depth program that I'll be linking later that you can also do it with.
2. as I mentioned, UNLZ updates the graphics, type resistance editor handles the actual in-game type editing. the type resistance program can be downloaded here:
http://www.pokecommunity.com/showthread.php?t=188426. dunno how exactly you change the graphics, though...
3. advance text helps you out with this. can't find the original thread for the program, but a quick google search should find you the program pretty easily.
4. Same way as mentioned in #1, the same program can edit both.
still, I personally use a program pack for my stuff, which can be downloaded from here:
http://www.pokecommunity.com/showthread.php?t=299112 saves me a massive amount of time and headache. it contains the attack editor I mentioned earlier, as well as a pokemon stats editor, and a few other programs that can help out.

While there is a decent amount of trial-and-error related to the programs themselves, most of them should be fairly evident on how you are supposed to use them.
There are some other programs that I didn't mention, such as advance map and advance trainer, but they should be included as downloads in the pack. however, one that isn't is a hex editor program. dunno on how you can get one, but you may need to go into the hex for some things.