Have you ever considered doing some of the work yourself?
I am only a novice home mechanic and I replaced a ton a my mercedes that I never thought I could. These things are built to be worked on...
1) A radiator is about $225 and requires removing a few easily accessed bolts and two very simple trans lines. The first radiator I ever replaced was on my 124.602 and it took just over an hour
2) I am not sure how much a starter is... $250 sounds high.
3) I am not sure what you are including in your tune up. If you DIY... oil ($15) filter ($10), air filter ($15), trans fluid and filter ($35), rear axel fluid ($5), spark plugs ($12), brake and PS fluid ($10)... well I am at $107. I guess you can get to $250 if you are replacing your cap, rotor and spark plug wires.
4) Rear shocks are $100 ea and have a bolt below and one in the truck - 1 hour job. If you are doing all the links it can get messy - but I think it is pretty straight forward. Again, I needed it to the rear sway bar links on my 124 and there was not much to it.
-justy a thought
1996 (W210) E300D 86K - Traded in for a Lexus
1992 (W124) 300D 2.5 Turbo 202K - Sold
1983 (W123) 300D, 146K - Sold
1970 280S, 263K - Sold - Beginning of addiction