how hard to change O2 sensors

they can get kinda stuck...such that the special socket that you bought for the job simply bends....so you break out the largest ViceGrips and a Hammer and break it free...one of the reasons that these are tricky is because they get heated with every use....usin' a torch on them would be practically useless~ They are not all/always tricky...just the one that you've got a schedule to keep~