Spend the money on the headlight rims, $70 is cheap. List is more like $120. I have a cracked one I've not replaced for the same reason.
Your tranny starts in 2nd gear unless you floor it HARD and hold the kickdown switch under the accelerator down or start off in 2 or 1 rather than D on the shifter. It is shifting normally.
Sounds like one of the gears on the seat is broken, haven't had this trouble myself.
I bought an 88 300TE for my mother three years ago with 196,000 miles on it, and I found that the vac lines in the engine compartment were all bad. Replacing them helped with tranny shift feel, rough idle, and serious heistation on takeoff (I have a rough idle problem again, but I think its something new related to the fuel distributor). I also replaced the idle control valve hoses and cleaned the idle control valve to fix an intermittant stalling problem.
I've recently replaced engine mounts -- made a huge difference, and isn't very hard to do.
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!