Thanks again Dale for your input.
Over the past couple of days, I have read through many many pages of threads (even the one with Mr. "reset the transmission learning, it fixes everything.").
This thread has a great explanation.
5R55 Repairs
He suggests removing the valve body and replacing the "3-4 spring." Would replacing this spring be a good fix while I have the pan off and replacing the solenoid? Or is he working on a different version than what is in my '04 V8? The manual says that you need 2 "aligner tools" to reinstall the valve body. I could only find 1 on ebay at $40. Yikes!!! Unless someone has a couple they want to lend me....
I will be ordering/have ordered:
1) Motorcraft reman solenoid that comes with a lifetime warranty
2) Special nipple insert for refilling
3) Filter
4) Maybe new pan gasket...just in case something is wrong with mine but I am not leaking anything.
5) a set of metric flex-head combination ratcheting wrenches to get at the 10mm bolt, probably cutting the wrench to make it work.
6) the "3-4 spring", if you all think it should be switched out.
I also saw the updated $209 servos. Those look like a great upgrade but their site says you have to partially remove the tranny to replace them.