sorry to hear about your troubles on the trans, that really sucks! First, on the SCA's local parts stores dont carry them it. If yours are anything like mine here, I know the dumb look you got. You gotta go to, sometimes, Ford dealerships, or Big rig dealer/service places, or big rig parts shops like Fleetpride. And I dont know if you have any, but get the test strips as well, and test it before you add any SCA's (A.K.A. DCA's).
Second, on the trans deal, I would ask some questions to the seller, like who is the mechanic, and is he an Automatic trans certified rebuilder, ask for a phone number to him as well. E4OD's are way to screwwy to send to someone who doesnt do it FULL time. I would see how much he is willing to pay for the rebuild, sounds to me like quite a bit, but Id stick with the well known 1500 dollar shop personally. Also, there are some updates on this trans. I do not know what they are, so ask around, either here, or the shops.
Now when you get er rebuilt, Id do 2 things. 1) add an external cooler if it doesnt already have one. 2) while the trans is out get yourself a Sonnax ( Blackclouddieselperformance.com ) calls it a "Tricumulator valve" I have one for my 92 but havent put it in yet, I'll get you the part number if u want. its cheap for the added piece of mind it gives you, sposed to firm up the lazy a$$ shifts and increase holding capacity of the bands.
Oh also, Id also ask the shop that says they can hop up the trans. with these componants, and those fancy thingamajigs over there. Just what exactly they are supposed to do, what is it exactly, and who makes em.
a good story of this is a local shop here (now outta business, go figure) called Jacko tansmissions (hehehe I call em somethin else, ya'll probly know what!) Rebuilt the same trans, 4 times in 3 years! on a truck that see's maybe 5k miles a year! supposedly they did this and did that, yeah right
well the last time they rebuilt it was for free, cause the converter exploded again (NOT REPLACED) and took the trans with it, not even a month after the rebuild. At 1800 green backs each time.
So anyway ask all sorts of questions before ya hand it over to just anybody!