Ford Repair: Transmission Solenoid, high mileage, valve body

Question
I have an '02 Ford Explorer with a 4 speed auto transmission.  Around August or September, it took a few seconds to go into reverse.  Since then, it has done the same thing maybe a total of 5 times.  About two weeks ago, the transmission started slipping between 1st and 2nd, 2nd and 3rd.  I took it to a shop and it didn't do anything wrong so they told me to keep driving it and see what happens.  I drove it a couple of days, maybe a total of 50 miles, and it slipped occasionally.  Finally, the OD light started flashing and the code came on indicating a bad solenoid.  I took it to a new mechanic on recommendation from a family member and he told me that instead of replacing the solenoid, I need a new transmission because it was "ignored too long" and "wore down the gears".  This doesn't seem right to me since I really didn't drive it that much and, when the transmission did slip, it wasn't really a rough change with a clunk or anything that would make it seem like damage was being done.  It would shift back and forth a few times before settling into the gear so I could understand the parts getting hot, but I don't know if that alone could ruin an entire transmission.  My gut is saying that this mechanic is just trying to rip me off but I just don't know.  Do you have any advice?

Answer
the problem your experiencing is, your correct faulty solenoids in the valve body. this was a fairly common concern, first i need to know how many miles are on the vehicle. if there is high mileage. replacing the valve body may only be a temporary repair as through normal wear and tear the transmission will eventually need replacing. if the mileage is fairly low- 70,000 miles or so, replacing the valve body should take care of your concern... you can actually google this concern and reference where others have turned and what their decision were.