1. Spark plugs: I checked the gaps in all plugs and ran into this problem: Plug No.2 was almost impossible to get out. I used a braker bar, penetrating oil and hot engine (cold did not work at all), and this was the only plug which only came out with hard work until the final exit; after gapping, it did not want to go back in, either, so I only screwed it in about half way, and it was tough all the way. Now that I bought new plugs, what should I do? If this was the symptom of a cross-threading, I rather screw the new plug also only half-way in and not have the expense with heli-coils, etc. Is there anything major wrong with this approach? The car is not driven very much. By the way, the threading of the difficult plug did not show any signs of damage/stripping or dirt, so I assume whatever damage there is is in the block, and a new plug will also stay in tight.

2. Anti-freeze: A couple of years ago, an independent shop specializing in Mercedes replaced the radiator with a Japanese, generic one and used Peak-anti-freeze (the green stuff) to fill it back up. When I asked about Mercedes' anti-freeze, they just made fun of it, saying that it is a scheme to make more money, that the green stuff also has all the protection additives for all the metals used under the hood, etc. What is the final wisdom about this? What chemicals would Mercedes use that nobody else does? I am coming up to a renewal of the coolant, what should I do and why? Somewhere I saw a reference to a cheaper alternative, Zerex-brand from NAPA and Autozone and the containers don't say anything really different from Peak or Prestone, anything else?

3. Brake sensor: One front brake sensor wire is broken off too close to the caliper to fix the wire. I assume that this does not affect the ABS, so I should be ok if I check the pads every couple of years. Anything wrong with my thinking? How could I reattach the wiring?

4. Distributor: My shop manual shows a vacuum advance attached to the distributor, but there is nothing on the car, and nothing seems to be missing. Do I have the wrong distributor?

5. Timing: The timing seems to fluctuate a little; it was a lot worse before I found a broken vacuum-thermo switch (50 degrees) and replaced it. Is there another place I should look for something wrong?

I appreciate any good advice.