Is it really time for my 91 Leggie?

Please read my original thread/story at: http://www.ultimatesubaru.org/forum/showthread.php?t=18046

I think my tranny is really/finally going as it's getting worse. I thought I've fixed it as the above thread proclaimed. But like a cancer, just when you think it is contained, it fights back and you might end up losing the battle.

The more questions I have are what seem to be the last resort without buying a new/used tranny. Are there any user replaceable o-rings inside the tranny? I know if it requires opening the tranny up, I'm not gonna do it as I have too limited knowledge on tranny. I remember seeing an o-ring on the long shaft (don't know what's called) that is plugged into the TC and goes in all the way into the tranny from the front, this o-ring is replaceable. The O-ring is close the end of this shaft. The question is: If this O-ring goes bad, could it cause what I've described throughout the above thread (particular the latter part after replacing the TCU)? Or could it cause the tranny not to have the pulling power it onced had?

Thanks in advance, guys.