No idea how long the sensors last. Mine are still original and still worked. I did use a new set for the new wheels since the stock wheels will be used in the off season. The tire guy had no problem installing the sensors. As yet my TPS system is not working. I have to take it in to have the dealer calibrate them. I am assuming this will be an easy deal but won't know for sure until it has been done.

The wheels are attached to hubs with lug bolts. If you are expecting to take off the wheel and find studs sticking out that you can screw your new nuts onto, you will be surprised. Your existing lug bolts might work since you are going to use a spacer. Without the spacer your lug bolts will interfere with the parking brake. Your existing bolts were not intended to be seen. They have a nice ugly rust free finish. Go to your local tuner shop and tell them you have an SLK and they should be able to fix you up for around $50.

For more info on lug bolts just search. Surprised me also.