2002 Durango 4X4 5.9L

OK getting the P1281 code on my check engine light. Cleared code. It is saying that my engine is running to cold for to long. I watched my temp gauge and it barely got into the normal op range area (barely above the section marked low, like right on the line) I drove for about 15 miles and it never got any hotter. I now know I need to replace mt Thermostat as it is obviously (atleasat I hope this is it) sticking open or is leaking through, either way it has got to be replaced. Lets hope this fixes the problem.

First issue: Will driving with the temp low harm my engine?

Second: Should I just go ahead and put in a 180 Thermo or the stock temp of 195?

Third: Do I HAVE to remove my alternator to do the swap or can I just suffer the knuckle knocks and do it with everything on?

Fourth: Should I just be lazy and let a shop do it? I would not think it would be more than $50 to $70 as it should not take more than 30 minutes for them. Yes I can do it... YES I am getting lazy in my older age...
YES YES YES Iknow it would be cheap and not terribly hard to do it myself but I have had a couple long work weeks and do not want to do anything on my next couple days off....LOL