Replacing oxygen sensors 1999 c1500 suburbandr

[ramainn]

I have two bad oxygen sensors in my truck with238,000 miles. Never been replace and am wondering how hard to replace. HVe watched videos and seems easy, but I wonder if sensors are frozen in place and hard to break free. I want to replCe them myself. Also, should I go ahead and replace all four?

 

[zora]

whether you replace all four depends on what the error code is, what is it?
can they be frozen yes. They also make special sockets to remove them.