1992 300sd diesel stall after start
 

I have inherited a 1992 Mercedes 300sd 3.5L diesel that has been poorly maintained that I would like to get running properly. Firstly, I discovered the air filter had not been changed since 2006 according to the date on the rubber seal on the filter and the large pile of debris that fell out when I pulled it. Secondly, the fuel filter looked like it hadn't been change in at least that long if not longer (inline filter looked ok). Anyways, the first issue was it would not shift out of third gear sometimes and would just stick. I figured it was a fuel or air delivery issue and changed all the filters, air and fuel and it fixed it. Then after a month, it started getting real cold and the car had trouble starting and the glow plug light did not come on until after the start and there was lots of smoke. I followed the diagnostics on the forum and found number 2 glow plug to have failed. After replacing it, the light comes on as it should and it was starting fine until this week. Now when I go to start it, cold or hot, it will spudder and run for a few seconds and die. I have to put my foot in it to get it to run and after it revs up it will idle and runs fine. I also had a draw on the battery which killed it and not to my surprise the wrong battery was in there with low cold cranking amps so I got the correct one. The stall out issue at start is still occurring, what do I do? I am prepared to remove the intake manifold and replace the remaining 5 glow plugs as well as clean the intake manifold as it is probably never been serviced. I have additional fuel filters and will probably replace them again as about 5 tanks of fuel have been run through the latest filters. I also did a diesel purge when I replaced the initial filters. I know this is a lot but I wanted to explain the entire story. What do you guys think? Where should I start?