You don't need to take off the heads to do a cam. However taking them off and sending them to machine shop to be cleaned up and have the new springs, retainers and valve seals installed is the way to go if you have the extra cash. The rear seal is for the crank not the cam. CPS is a crank position sensor. You can install a cam without changing bearings however if the bearings are worn you may want to replace them. This is not an easy task by itself because they are pressed in and when removed could leave metal particles in your block. Most people who replace cam bearings send the block into a machine shop and do the entire lower end. Do you have a mechanic helping you with any of this? Everybody on here says to add a cam instead of rockers however changing out a cam is not the simplest thing for an inexperienced person. A bigger cam with throw a random misfire code and require programing your PCM also. I'm not trying to scare you but there is a little more to this stuff than some on here will let you believe. An option to the cam with almost as good results is 1.9 rockers instead. You could take off the heads and have the machine shop clean heads and install springs. It's possible to drop a valve in the cylinder if a person doesn't know how to changes springs while the head is on the block.
