Date registered: Apr 2009
Vehicle: 2007 E350 Sport, 2007 SL550
Mentioned: 0 Post(s)
Quoted: 30 Post(s)
Forgive me if I'm guessing wrong, but I'm guessing you have limited automative service and maintenance experience, and I'm guessing you have no more than perhaps a few basic tools: a few wrenches, some screwdrivers, a crescent wrench, a vise-grip pliers, and a hammer--everybody has a hammer, or a good hammer substitute.
If the preceding paragraph is totally incorrect, then don't waste time reading further. But if it fairly summarizes your experience, your competency, and your toolkit, then I respectfully suggest that you take your car to an MB dealership or a reputable MB service center and pay the tab for the new batts and their installation.
In addition to buying new batteries and having them installed properly, you'll buy a helluva lotta peace of mind.
There are a lotta repairs and maintenance items I can competently perform myself, but I know (more or less) my limits. I observed an MB battery replacement once, and that prepared me for replacing my batts later on. And I could and likely will do it again. If you were my neighbor, I'd invite you to drive your car into my garage and you and I together would replace both batteries.
So ... I'd hate to see you short out your new battery or mis-connect something while you're squirming around in the deep recesses of the trunk. Pay to have it done by a competent technician. Good luck.