It's really not too hard to crack open and inspect, just a few things to keep in mind about it. $50 is an awesome price for someone experienced to look at it. Checking for shavings in the fluid would be a good idea, but also know that there's a magnet inside that catches it. Check out my pics on the "proof" page in http://yrethguad.tripod.com/wrongedbycottman to get an idea. If there's shavings in the fluid, the magnet must be beyond full, and there's not much metal left on the gears and such.

There should be a nice sticky thread on honda-tech for all the tranny codes. I know I had to look it up at one point to find out mine. Or maybe I searched there.