Trans fluid exchange again and again ...

OK guys I've read over the trans threads and seen all the opinions. I have just made a deal to buy a '99 Jimmy from my boss. It hasn't been beat and has 80k miles. He's had it since about 10k and never serviced the trans in any way. I have to tow a small (17 foot aluminum) boat over a big mountain a couple times a week. My plan is to have a fluid exchange done at Jiffy Lube, making sure that it is a passive process using only the trans pump to move the fluid out of and back into the trans. I will also make sure they use only the fluid recommended for this trans. I plan to drive it about a week and drop the pan and change out the filter and top off with the recommended fluid. Before I start towing the boat I will add the biggest trans cooler I can get in the thing.
I have a couple of questions for you guys, since you really do have a wealth of collective knowledge.
What would you do differently?
Anyone done the cooler thing and have a good one to recommend?
I have heard of guys routing the cooler from trans to cooler and back to trans bypassing the radiator. The logic is that the radiator adds heat to the fluid instead of taking it out. I have one friend who is a retired tech from a GM dealership with all the certs, and training for trans and cooling systems who says this might make sense. It scares the crap out of me. I think I want the assurance that the trans fluid can't get any hotter than the radiator coolant. Anyone got any thoughts on that idea?
Lastly, I think I'd like to monitor this trans temp, can anyone recommend a stick on, glue on temp sensor for this trans pan that is at all reliable. I can get a half coupling welded into the pan for a regular sensor but I really don't want to unless I can't find an easier alternative. OK guys, thanks in advance for any suggestions you can give me.