I've just started hacking mine, but I can offer some advice.
A good DMM is critical if you are making your own cables, tape needles to the probes to get at the bios chip and pins on IDE cables.
If you are taking the converter to custom 3.5 cable route, an automatic stripper will be very handy, plus you can strip the cables in pairs with one.
Buy all the parts at once from the same place to save alot of money on shipping (This was supposed to be a failry cheap project... I was wrong)
Don't waste mailing lables on getting that crap left behind from the silver sticker on the back, use regular packing tape, works in about 2 pulls.
De-Solv-It can get rid of any leftover residue, or adhesive you might find.
The srew things on the par. port will be superglued (That blue crap) use the right size nutdriver type tool. V4
If you cant find a screwdriver that will work to get those torx out, buy an eyeglass repair kit, it'll be the right size. V4
For pre-buyers: If you get asked TOS questions, and are paying cash... have fun with it! Make up a new name, address ect. Just be sure the zip code matches the town you give them and state. :)
This messageboard is NOT the only place for info, I frankly have found some better sites, just visit everyone's links page.
Don't forget about reversing the mouse and KB on your PS2 adaptor.