first - thank you for the time you're taking into making sure that I have details that I will need. I can't think of anywhere else where I could get this kind of information from a source like yourself who has the knowledge from pure experience gained strictly from doing it personally & perfecting it.You're welcome.
There are many other things you'll need to correct/replace, especially at the amount of milage on that transmission so I'd just overhaul it (see my list as it has everything you need)....The level of effort isn't really that much greater and you know that you're resetting the clock back to zero when it comes to the unit's age. If you're going to go through all the trouble acquiring the tools, knowledge and setting aside the time, I'd just do it right all at once vs piece-mail.
Reinforce the welds in your existing drum (or have a machine shop do so) and purchase the Sonnax 1-2-3-4 billet piston. Also, if you have an early 6L80 then your pump has a first design stator. You will want to swap to a 2nd design (mid-year 2009+) that uses the updated sealing ring set up (locking sealing rings and underlying support O-rings) to prevent slipping/flaring or other symptoms driven by inadequate apply circuit sealing (aka cross-leaks) between the pump and 3-5-R drum.
I swap in a 2nd design stator/pump cover assembly on all 6L80s that come in w/that first design stator. If your vehicle is pre-2010, chances are you have the first design. Make sure you have your pump body/bell housing machined as well. Rotor and slide should also be replaced at this point (your machinist can source them for you and machine everything to spec). Install Transgo's unbreakable pump ring kit with new vanes for added insurance.
First design is on the left, second design is on the right. Note the square notches machined into the sealing ring areas on the pump at right. The early (left pump) does not have these.
View attachment 401102
im gonna follow your suggestions thru this ... I am admittedly pretty good at knowing when there is an area in which I don't yet have the skill or knowledge to tackle it without significant risk. I am slow & patient with myself in learning & educating & studying whatever part I'm working on until I feel confident enough that I can take it on. I also don't have any issue in humbling myself & reaching out with questions. you may get a lot lol.
could you give me a rough idea of what in this rebuild / over haul process will be something as a DIYer that I will have to enlist the help of a shop? is there anything that I just absolutely won't be able to do & will need to go to a shop? or will I be able to tackle it - given i have the right tools ? orr is that unrealistic due to some of the prices & being that I will only need them once? hope that makes sense.