my smog pump is now making bearing noise and the belt squeals when the truck sits for over 5 hours, but then goes away after warm up. I am thinking the bearings warm up and then run fine. I just bought another pump that i want to take with me to CMCC just incase the other one s***s out on me. Would i be better off changing it out before i leave or change it out when the other one craps out? how hard a job is it to change out?