You're 100% right bill! I ended up using this tool in my shop press and basically just used the press to push the tool down rather than deal with the threads, and that works for me, but now that I look at your extension, I think that would be a much easier way! Luckily the snap ring and compression on that clutch spring is pretty low from what I remember so it's not that bad either way. I would say to try Bill's extension method first though because it's probably vastly easier to grab the snap ring without the press being in your way.
As far as the kits, this is the kit I've used a few times:
https://www.ebay.com/itm/4T65E-2004-On-GM-Tap-Shift-Super-Master-Rebuild-Kit-With-Pawl-Lug-Input-Friction/272494991653?epid=672397377&hash=item3f71f79925:g: 5lAAAOSwNSxVCzs8&vxp=mtr
Along with:
4T65E Transmission Solenoid Kit Set TCC, 2 Shift, EPC, Switch 2003 UP 84420AK | eBay
I also recommend at the bare minimum for the valve body:
GM 4T65E Transmission AFL Valve Repair Kit | P1811 Code Stopper | SUPERIOR K098 | eBay
If you really want to future proof your rebuild, I'd get this instead of the above afl repair:
Sonnax SC4T65E Transmission . 4t65e 91-99 | eBay
The last link includes the lube tube retainer along with seletable shims for the thrust clearances. A lot of rebuilders neglect to check this movement, but it is discussed in the video manual I cited.
These are what I use in all my rebuilds partly because I like to fix it once and fix it well rather than doing it again in a few years, and partly because I'm ocd. Take it as you will. Personally, I don't think $500 is unreasonable for parts cost to get a transmission that will likely outlast the car.
One note, while not always necessary to change, the kit does come with the case bushings and such that need to be pressed in. I got lucky and used various sockets with my shop press to install them and it worked, but it may not always work like that. I'd check them and if you can't catch your fingernail on them, you're probably good to go.
The one bearing I highly recommend replacing is:
Amazon.com: AC Delco 75086 BR Needle Bearing, Converter: Automotive
As this bearing is known to grenade with age. It is press fit, so removing and installing will require a press, but most shops don't mind doing this for you for a small fee.
I usually clean and reuse the other needle bearings. The video goes over how to properly clean and inspect the bearings.
Sorry for the long description, but hopefully that helps!