Well my EF II ghia has a very aggressive stutter that started out when cruising at around 2000RPM and now happens at idle.

It happens once every couple of days and basically when I'm idling at the lights the idle will almost drop to zero and the car will then jolt straight back up to idle speed and then repeat this cycle for a couple of seconds.

The car also has a lot of problems with the gearbox, sometimes when stopped in gear/drive, the car will somehow just disengage and the idle will jump to 1300RPM, I need to put my foot on the accelerator and hold it at around 1800RPM for a couple of seconds for it to pop back into to gear.
I'm planning to replace it soon but was wondering if this could be causing the car to stutter?

The car has been fully serviced (all filters and the usual replaced) as well as new thermostat, oxygen sensor, leads.

What should I do?

if its been fully serviced with plugs and leads, fuel pump could be causing some of your dramas or injectors?

Sounds like the idle solinoid is stuffed. Its a common problem