Starter Solenoid problems of the 1999 Ford Explorer

I purchased my 1999 Ford Explorer in may of 2004 and within a month, I began experiencing problems with my transmission. More specifically, the vehicle would loose power while driving, the transmission could be heard shifting and also shifting movement was felt while driving. I took the vehicle back to rio valley in espanola, new mexico where I paid cash ($8700. 00) and was told that I did not purchase the warranty and my vehicle needed a new transmission and it would cost me $3200. 00 to have it repaired. I complained and was told that my gasket was sealed with a sealant that went in to my gaskets and damaged my solenoid. I has just taken it for a transmission oil change and thought well that could be, however, after talking to the owner of hindi's oil stop, I felt certain that this was not the cause. Rio valley Ford did clean out the transmission a couple of times and charged me $340. 00 and I was told that this was basically going to have a band-aid effect and I would ultimately need to get my transmission fixed. It was getting me around for awhile but lately the same shifting noises and feelings I had heard and felt are recurring. My overdrive light also goes of and on continuously sometimes while I am driving the vehicle.