'88 300Se stalling

[prmike1965]

I have a 1988 300se with 187,000 miles on it,(bought on E-Bay) had the head replaced 8 months ago due to worn guides. now, the car will not stay at idle at times, and when i let out the throttle to turn, it stalls. i replaced the cap, rotor, wires and plugs w/ OEM parts. At times, i will turn the key without touching the throttle (approx. 7 times) and it will start fine, then it will go back to not idling or it hesitates bad when starting out. I have replaced the idle control, (E-Bay) it ran fine for 2 days then back to the same old headache. i love this car and want to keep it, i want to DIY, but i am intimidated to DIY because it is expensive to r&r parts just to troubleshoot. also, will buying a CD repair help, and where can i get one?