If your steering wheel is out of center (to the left) and it doesn't matter what road you are driving and where the wind comes from (steering wheel stays left from center), I would try an alignment.
You can start changing the front tires yourself, but personally I don't think it will help you that much.

BTW: The rear wheels can cause an out-centered steering wheel and pulling to one side as well.

greetingz,

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1990 300SL-24
1993 C250D with a minor 600+k kilometer
www.MBenzNL.com(the Netherlands)