
If you want to give the aftermarket guys a try I'd not only stress how perfect of a job they need to do
without cutting/butchering any of your wires, but get it in writing that any faults caused in vehicle by the install will be fixed if not by them then by the dealer at their cost. (if it doesn't go well, but hopefully it does)
I think I remember some members on here having remote start installed, but don't remember who or what problems they had if any. Hopefully they will all chime in.