Do I need to replace head gasket?

A guy rebuilt my 1981 KZ1100A Motor(valves,seals+springs;cams re-ground,hi-dome pistons and fresh ring sets),all valve lashes were set,and cams timed.I was going to put the valve cover on and put the motor back in the frame,but discovered that one of the spark plug holes is stripped-out and needs to get a heli-coil(one cylinder already has one in it-and not the good kind I guess-it came out with the spark plug).Do I need to replace the head gaskets(2) and o-rings again?(I hope not,as they are expensive).Also,I have heard that the Heli-Coil brand of thread inserts is better,because they lock in place in the head,and will not thread out with the spark-plug,like the one I already have an insert in did.Does anyone have any knowledge of this?If I have to replace them(gaskets+o-rings I guess I will-I want to make sure it is done right!Thanks to everyone!Here is a pic of my bike.

I would replace the gasket. I think it's maybe $50 for OEM, cheaper for aftermarket. I would do it for peace of mind because I don't know what the previos builder did. If the cylinder/head surfaces were DEAD clean and smooth, you might be able to get a seal with reusing the gasket but not if there is anything on it. If you do reuse it, use the copper spray gasket sealer but I wouldn't.

I'll pipe in, now there are 2 common sizes of solid inserts, this is the outside diameter. If you have the smaller of the 2, which I believe would be K&D tools USA. If the larger it would be from Heli-Coil, as they provide solid inserts as well. You didn't say if the thread in the Head is bad, just that it screwed out with the plug. This can be reinstalled if the thread is good, Loctite red high temp comes with these inserts, and the spark plug should have anti-seize on the thread as the plug is the install tool. You can buy a new insert easy enough which ever size/ brand. Other option is the wire Heli-Coil, but I can't be sure about the Tap used is the same or not. I think it's the same for the Heli-coil brand, 70% sure.
Anyway you shouldn't have to pull the head at all, there is even a larger outside diameter insert used for the 6litre Ford V10 engines, same 14x1.25 inside thread.