Error Code PO753

OK, This is my first real problem in 4 years with this Blazer. Long story short, I need help narrowing down a SES light code of PO753. I know it has something to do with the Trans., but have been given several possible causes by the parts stores. Autozone says the shift solenoid, and they have 3 different listings ($45; $26; $30) and they did not know which one, or where they were located (Haynes was no help). Checker had same code but said it was Trans. Modulator ($140) and could not tell me where it was. The reason for this issue is that my wife drove about 200 miles in 4WD, and didn't realize it. She called when the SES light came on and told me there seemed to be a loss of power. I had her check the usuals (oil, trans fluid, coolant, etc) which all came back fine, so I told her to drive it home and I would look at it when she got here. She arrived, and I took it for a drive and about 1/2 block away realized it was in 4WD, Took it out, and seemed to fix the problem, except the SES light stayed on, and the shift points for the trans seem to be off. Any help would be great, and I will be watching the sight most of the day.

Hope it was in 4wd Auto or Hi at least. Reset the SES light and see if it returns as when in 4wd the trans changes shift points. Check the transmission fluid and make sure not burned and brown as may have gotten pretty hot - if so a pan drop and filter is in order.

It was in 4Hi. How do I reset the light?, and the shift points in 2Hi seem a little off, or sluggish. The fluid seems fine, but was planning to change it and filter anyway. One of my problems is which of the shift solenoids to change? If I remember right, there are 3 and all of the parts from autozone were not listed as exactly shif solenoids.

Is this the correct solenoid?

http://autozone.com/R,APP909128/vehicleId,/initialAction,partProductDetail/store,/partType,00623/shopping/partProductDetail.htm

and are they both the same part number?