Mercedes: eletric welding on merc e200, electric components, standard precautions

Question
if the battery is not connected will i do any damage to any electric components or do i need to do anything else

Answer
William,
I would also locate the computer and unplug the wiring harness there as well. Any voltage surge could cause problems. Be sure to connect the computer and then the battery Positive first then negative.
The standard precautions about isolating your welding from any potential flammable materials apply. Remember that foam cushion are just like jelly gasoline and the smoke is quite poisonous.  Using good ventilation and making sure there are not fuel fumes is also important.
Lastly, it is also a very good idea to connect your ground as close as possible to the welding position. This process helps keep the potential for static charge on the vehicle to a minimum.

Good Luck, let us know how it turns out.