Yes stay away from LMS. I would not let them tune my lawnmower.
You seem to have a pretty good plan. Personally I would change all of the fluids in your car asap. Oil, coolant, PTU, RDU, and I would start trans fluid cycling. 5 out and 5 in.
I would also check out the first couple posts in this thread as well. It will answer a lot of your questions with fluid swaps, mods, installing tunes, ect. I am working on bringing all of that information here as well so please excuse the link to the other forum.
https://shoforum.com/index.php?threads/sm105ks-ownership-performance-maintenance-thread.138235/I cannot recommend a garage where you are because I live no where close to you. If you were in AZ I would offer the install your parts. Hopefully the other members can jump in and help you with that.