I just finished rebuilding my cylinder head two days ago and found that it was fairly easy to do. I rebuilt it because of bent valves. The timing belt didn't break like I hear of other people, but a careless mistake when replacing the original belt on my car. Turns out that in my car, the crankshaft pulley helps to lign up the belt so it doesn't slip off the camshafts, water pump or guide pulley. I installed the new belt and started the car without the crankshaft pulley just to see if everything was installed good and the belt slipped and bent the cylinder head valves. Anyways I got a hold of the service manual for the aveo 2004,2005 and 2006 aveo motor and followed the instructions on disassembly of the cylinder head. The hardest part was removing the valve spring keepers. Anyway, I had 155k miles on it and now it runs like new. If anybody is interested in the service manuals please let me know and I will forward it to you. It includes the electrical wiring, exhaust system, break system and various other material that someone put together.
Repair shop quoted me $2500.00 for the repair and I did it for $800.00. I spent this much beacuase I went ahead and replaced the oxygen sensor, water pump, pcv valve, map sensor and bought new spark plug wires from the dealer just so it could be original OEM parts. Car runs like new again and I feel proud running it again since this car went 155k with no problems what so ever.
Eric