I have a 1989 300te...the doors are manual (I put the key in, doors open)...are there any 'quality' remote systems? My mechanic says they all suck! They all are ripped out by him...stating "They all lead to trouble!"

No they don't all suck.
It only as good as the guy who wires it in whether or not he does the job properly and how familiar they are with Mercedes.
Some guys hate them because they are not good at wiring.
The older units wre bulky and required too much wiring to tap into.
The newer units are smaller, and require less wiring and have more ease of installation.
I installed one in my truck and on many mercedes throughout the years with my brother in law in his gadget business, and they are very reliable.
We get a bad control unit from time to time, but usually after years of good use.
Rec-11 units are good and inexpensive.
Call Jim LaPlant (Atlanta) 404-277-9383.
He can answer every one of your question down to the wire, color, location, and what unit to buy.