the HUD problem is common. one of the diodes on the inside needs to be re-soldered.

the easiest way to change the SC oil is to take the blower off and tip it upside down then refill it with a whole bottle that you can get from GM. you cannot get boost in idle, there is no load on the engine.

usually a stutter is a missfire. change out plugs and wires. if that doesnt fix it look into the coil packs and ICM. if the idle is jumpy, you might have a vacuum leak.