Distributor hold-down bolt is a 6mm (I think) allen head straight down on the right side of the distributor. Takes a LONG allen to reach it, the standard size is too short. Long T-handle is you best bet. You cannot get it out with an allen 3/8 or 1/4" drive, either, no room. The bolt sits in the adjuster slot, you cannot mistake it for anything else.
Once you have the bolt out, the distributor should slide right out. However, if it is really stuck, run the engine up to operating temp with the bolt in place, then try, it may come loose. I've not heard of them sticking, but anything is possible. Penetrating oil is the next step. Spray it all round the bottom of the distributor, then run engine (with bolt in in case it comes free!) and then try again. GENTLY tapping with a soft mallet may help. Don't use a steel hammer.
You don't actually have to competely remove the dist., just loosen it and lift it enough to get that top bolt out. Stupid design, if you ask me......
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!