1998 GMC C1500 Timing

I have a 1998 GMC 1500 4WD pickup with a 5.0 L (305) engine. I was just replacing the distributor cap, rotor, spark plugs, and wires when I noticed that the distributor (that actual part that goes into the intake manifold and down into the oil pump) one of the "ears" that is threaded that the cap gets bolted to was broke, so I had to remove the distributor shaft from the intake manifold. I have now put it all back together and the timing now seems off. The truck runs but it "spits and sputters" when you put it under load (in drive or reverse). Under the hood it says "engine spark and idle speeds are automatically controlled, do not attempt adjustments". Does this mean I need to take the truck in and have it serviced and hooked up to a computer or monitor to have the timing fine tuned?

Shawn S.