94 Camaro 3.4L

I was doing a tune up today first time on this car but not my first time , I started with the left side ( the hard side ) got them out easy , then started on the easy side , got the first out on the right side , then went for the second I noticed right away when I went to break it loose it was already loose, so I thought to myself the guy I had do it before must not have tighten it up good enough , so I went to untighten it with my hand , im guessing he stripped it , because it wont loosen up or tighten up anymore , my question is does this just happen sometimes or did he jack it up by over tightening , and from the other stuff Ive read the v6 heads are made out of cast iron, so am I correct in assuming that its probly just the plug that is stripped? this is my first post and I'm not a auto guru but I have been doing oil changes and tune up for quite awhile, just basically want to hear what you more exprienced guy have to say, Thanks in advance for any info . http://camaroforums.com/forum/images/kirsch/misc/progress.gif http://camaroforums.com/forum/images/kirsch/buttons/edit.gif (http://camaroforums.com/forum/editpost.php?do=editpost&p=359528)