02 Ranger IMRC problems

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Let's start with, I'm a chick, I know the basics of cars (and no, not just what type of air freshener smells best...) I can at least change a tire and the oil....on to the problem:

I had my 02 Ford Ranger run on the computer because the check engine light was on (has been for 2 years, but suddenly started shifting hard...) the codes spit out are DTC 1537 & 1512, which says IMRC stuck open & IMRC stuck closed. How can this be? The mechanic says the IMRC needs to be replaced, is this the only option?

He also said the "arm" inside the transmission needs to be replaced, but can't say 100% for sure this is the actual problem until he's in there and sees what is going on. Been going to this mechanic for a while for my Honda and never felt screwed before. This time it's not sitting so well, cause the truck RUNS fine...

Thanks for any insight!