Hi people bran new to the world of Mercedes-Benz I'm looking to buy a SL350... now I've looked on a few sites and there seems to be a lot of issues with these beautiful motors down to door locks boot seals fuel tank issues doft door close ect... don't put me off tho... anyway I have a few questions on these I'm after one with all the bells and whistles you can say ... pano glass roof wide screen nav came in late 2004 I think full elect pack , 7G tonic transmission ect and the difference between the 3.7 and 3.5 v6 .. now question one if I bought a sl with out a glass pano roof can this be fitted after ? The Nav unit fitted to early sl 2002/2004 can this be upgraded to the wide screen nav late 2004 to 2009 models by swapping the head units and facial.. The issues what to look for 7 speed auto what year does this start from. and what do I need to look out for when looking at these cars as they are new to me mercedes Benz thanks again Steve...