The small amount of sludge you're getting in the pan is likely from the problem you're having. Everytime this trans is goofing up, it's take more miles off the trans til eventually the trans will need rebuilt. Need to get it corrected ASAP.
You've got nothing to lose by installing a kit at this point. It's either going to work, or it's not. And if the trans needs a rebuild, then you can use the same kit in the new trans or tell the guys to install the kit you just installed. Unless you do a mail order job, then just suck it up, let them install a kit and be done with it so that you don't have to open it up and void any warranty.
All this **** does here, is makes more irritated in my situation that I can't get set up and start building transmissions again. I am so rusty on 700r4's, and that Trans is the money maker now since there are so many out there along with the 4L60-E. A guy could live off doing nothing but 700r4 and 4L60-E's out of his garage. Special tools are needed and they are not cheap. I've improvised on some of them but to hell with that. I hope someday I get set up and get the special tools needed and can start building again. And then I won't be so rusty either.