To replace the torque converter solenoid you don't need to take the tranny off, but to replace the other 4 solenoids you do. So, if you have the skills to work with the transmission... In my case, I had a shop do that [emoji16]
I've done a lot of search in the web for solenoids, and the prices where about US$ 300 or more (the 4 solenoids kit) and US$ 170 the torque converter solenoid (if I remember correctly).
As I live in Brazil, that will result in about US$ 1000, shipping+taxes.
I ended buying from www.partsouq.com, which is located in Dubai. US$ 160 the kit, and US$ 95 the converter solenoid. Original ones.