Getting away from the window tint guys was a good move. I'd bet they would get 90% finished butchering the wiring before it occurred to them that a remote start wouldn't work on a diesel without some serious modification. Over my own objections, I put a remote start system on a 560SEL 7 years ago. I spent about a day and a half to get it installed properly... no "Scotch Locks" or cut wires, soldered connections at terminals, routed the wires along existing harnesses, etc...I thought I'd done a fine job of turning "chicken excrement" into "chicken salad". The customer had an absolute "cow" over the bill! The moral of the story? To do it right usually exceeds the cost(or perceived benefit) of the aftermarket system.
I would stick with the factory alarm. It's easy enough for anyone familiar with it to diagnose and repair. Besides,if somebody really wants to get in your car...they will.