I rebuilt my 2004r last year without a single special tool. All I did was grind a notch in a screwdriver and use normal hand tools and a yoke to hold and center the output shaft.
I went through Dave Husek out of NYC for my parts (Turbo buick performance). Pricey but everything is in stock and he is great at picking up the phone (sometimes it's hard to get off the phone lol). CKperformance is another commonly thrown around supplier but they are poor at shipping orders out complete and communicating what is in stock, unfortunate as they have great prices and a clear website. You can go with a normal kit from a typical supplier but piecing together the line boost valves for the pump, the seals, the bushings, clutches, selectable thrust washers, etc, is really hard if you are doing just a single trans. Husek knows what you need which helps a lot.
Husek is a firm believer in tweaking the stock valve bodies instead of doing a trans-go. I shipped him valve body and he drilled holes in the separator plate and inspected the valves and remanned. If you tell him what you are doing he will build a setup tailored to your setup.
I just put 500 miles on my fresh trans last week on a 3 day drag and drive with a 12 second full weight Cutlass and it performed flawlessly. It's my first auto trans rebuild. It blends street and track manners great.
And yeah, the $200 core is worth it. I spent $500 to buy a BRF valve body and governor from Husek as I started with a non performance core. Don't mean this to be an advertisement (I paid him probably 3x what I initially budgeted) but it did turn out great.
