I don't know much about your engine, but if it has a coolant temperature sensor on the head (probably 2 pin, light blue) a bad one could be the cause of your cold start problems.
The only other item you listed that I can speak to are the shifter bushings. This should be no more than an hour job, with parts costing about $5 (2 nylon bushings). If you are just a beginner DIY'er you could do this job. It's all done underneath the vehicle.
'91 300E, 210k miles