Thanks everyone for the great tips. I did manage to find where the spark plugs were with the help of you guys and the Alldatadiy data. I still haven't changed them as I ran out of time over the weekend. I plan to do it again this weekend after having the engine dead cold as suggested. I will also try the oil change now that I have an idea where the filter is (Alldatadiy was really not a help on this one with its poor illustration). I will check again the DIY section regarding the '95 e420 as it is close to mine as suggested.
I was able to change the rear end gear oil though. To my surprise, the oil was foamy and somewhat tan in color for the first few seconds of draining it. It seems that the oil was contaminated with water...I think! I replaced it with the Swepco brand gear oil, leftover from when my friend changed his 300e. Maybe it's all in my head but I noticed a little quieter rear?
BTW, the Alldatadiy info leaves a lot to be desired as it did not offer the collective tips and insights this forum is so great about.