Radiators and coolant
On the radiator Q, if your radiator neck has no steel inner liner (just pull the big upper hose and it s/b visible), and the PO used the green (or non-MB) stuff for coolant, consider replacing the whole thing.
My experience with rebuilt ones is that the re-crimped replacement plastic top starts to leak (2 data points - 300SD/1983 and 560SEL/1990) and use of non-MB coolant causes the plastic in the neck to harden and crack. Plus, many overtighten the hose clamps. Use MB hose clamps - they are slightly rounded to prevent cutting the rubber, in contrast to many non-OEM ones.
Behr makes OEM radiators - they are fairly inexpensive from Fast Lane. A rebuilt usually runs ~$100 if you pull the old radiator yourself. If you take the fan off (4 10mm bolts) you can change the radiator in <60 minutes. Put a piece of cardboard in place to prevent damage to the very delicate cooling fins for the a/c, and make sure you have the 2 rubber doughnuts on which the radiator rests - might make sense to get new ones at the age of car you have.