I change the oil in my car without a torque wrench, just be sure to use the new seal that comes with your filter kit from MB, don't use an aftermarket filter, you will notice it comes with a brass ring too for the oil drain plug. I use my hands and just loosen it, it is kind of firm but works. The seal goes in the cap, the new one makes it a little harder to screw back on, but just keep going until the lip hits the metal edge and you will be fine. I didn't replace the seal once and it leaked. The bolt on the pan is a 14mm, I think, a standard socket will work. Congrats on your Car! you will find it is a wonderful machine that gives you lots in return for you taking care of it.
Are you an MBCA member? If not join, you will get parts, and service at a discount, and technical advice for free. Go to www.mbca.org.
Regards,
Brian