Overall it sounds like a replacement is going to be the best route.
A soleniod is not too bad to change, but the side cover has to come off. (Did I really just say it's not bad to pull a side cover..I better check myself into a clinic
) Side cover is the painful part of the process. Gotta drop subframe and the side of the trans. Once it's off, the soleniod is a simple clip and it's out.
With your mileage on the trans and the black, likely it's best to replace the trans.
BTW, that's the fuel/rev limiter you are hitting at 6000 rpm.
