yep alan is right, if that 94 transmission is stock, it has the old fashioned metal piston anyways, and needs to be replaced with the rubber bonded one anyways.
I would order new 1-2 and 2-3 accumulator pistons, two valve body gaskets, a new trans filter, and new springs from dan. Mine as well drill the seperator plate while you have it all apart. I wouldn't mess with the od, its fairly easy to screw up, and not really necessary I don't think. No need to upgrade the reverse servo either.
All the parts I listed above are very cheap.
Get yourself a good pair of snap ring pliars, not a cheapo kind, and get youself either a piston compressor tool (well worth the money), or you can rig it with a bottle jack, I like the compressor tool much better.