You know the old saying, the only stupid question, is the one not asked.

I had somewhat the same experience. We bought a 300TD for my wife and I did lots of work on it. Felt so comfortable I bought a 300SD thinking I could transfer my knowledge to it. Well...not the case for many of the systems. So I began my learning process on that as well. I am real comfy with 123's and 126's now.

Welcome and enjoy your new ride!
Don

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1980 300TD-T (82 Turbo and Trans) 159,000 Miles "Jackie-O"
1983 300SD 272,000 Miles "Aristotle"
1987 Jeep Wagoneer Limited - keeps the MB's off the ice and out of the snow
1994 BMW 530it