Body and Interior Specific Aid

1989 Mercedes benz 300SE the seatbelt light that looks like airplane buckle up symbol now blinks constantly this is really weird could someone help me?

On rare occasions when I turn the A/C on and select high fan speed the blower is very fast (read powerful) and the temperature is very cold......Great! On other occasions in fact most of the time when the A/C temp is selected and the high speed fan switch is selected the fan is slow and the temperature is warm to cool. Yet at other times if I switch off the engine before switching off the A/C for example when refueling and then turn the engine back on the fan blows H-O-T.

Our 1979 300D runs great at speed. We just installed Kent's boost pump kit and it really does help starting and idling and did help a little on power too. I was hoping it would also solve our shifting problem as well but it did not. From a dead stop, the car will always start rolling in second gear (which as everyone knows makes it painfully slow) even if I mash the pedal down. It will do this even if I shift into neutral while stopped then shift to drive just before moving.
We've already done the following to this car: recent valve adjustment, timing chain replaced (has good timing now), recent diesel purge, new filters, fuel lines and fuel strainer, adjusted kickdown rod from throttle to transmission (which did improve the shifting above 20mph to earlier shifts for more power).

So my 240 has low oil pressure at hot idle. Kent's "Diesel Performance Tuning and Repair" says that this is caused by either worn oil pump gears or crank bearings.

I am currently unemployed so I'd like to try to fix this without a mechanic, but I love my car and I don't want to risk f*cking something up royally and ruining it. Would this be the kind of thing I would be able to do myself? I can already do basic stuff like changing oil and I've installed the glow plug relay manual override so I have some pretty basic experience.