Not sure on the heat as I haven't used the block heaters in my Diesel vehicles yet. FINALLY installed the one in my 300SD and the SDL one I didn't need last season (car was out of service until March).
Be sure to use the proper light yellow Xerex or MB coolant when you do the water pump. Do the belts since you're in there.
Another consideration, the M116/7 love to fail due to broken timing chain guide rails. If you haven't done them, I'd set aside an afternoon. The driver side are the real killer. Plus you get new gaskets too.
