400E - Flaring / Slipping Tranny... Toast?

[thesheep]

92 400e w/ 145k.

Bought the car about a month and a half ago.. CE lit up on the way home [about 250 miles]. Had it scanned, turned out to be the upshift delay valve? Cleared away for about a week. Came back. Shop discovered that one of the vacuum lines running to the tranny was broken, also suspect that it has aftermarket valve body. [A hunch, because it seems more eager to start off in first] Drives BEAUTIFULLY for another week. Few days later I'm driving home and in between 2-3 it flares out. Happened so fast I wasn't even sure I beleived what I just seen the tach do... Next day it does it 3 times on the freeway when I'm trying to pass, except one of them I punched it and it kicked down to second, the revs shot up to about 6k and then it chirped the tires going 65mph when it finally shifted. Take it in, they can't reproduce it. Still suspecting that it's this "aftermarket valve body". Suggest replacement.

Next morning, stick it into drive.. Revs up and slowly creeps around [grinding sort've noise being heard]. Manually shift to all the other gears, same thing, not sure it's shifting at all. Shift back to D and it seems to catch. Goes away for about three days.

Tonight on the way home from work it's doing it again... Talked to another indie shop, he's thinking that the clutches are worn out. Doesn't matter what gear I've manually shifted in, once it'll catch and get me moving it seems to subside, but it still kind've slips all the shifts more than usual.

Couple of questions.

1. What's a rebuild going to cost [of course I read about someone with this similiar problem where the gears were all chewed up and not at all rebuildable]?
2. What's a reman box cost?
3. What's a new box cost?
4. Anything else it could be?

Thanks guys... I miss my 400E already.