no you cant just swap one for the other. The first reason is that the photo resistors give resistance and by that tell the robot to go to right or left. With the emitter and detector you have to have the micro controller know that it needs to detect the ir light coming from you. it cant be a reading that tells it to go right or left.
the principle is they both will need different code to operate as they were intended. the $50 upgrade with the sharp IR sensor sounds like it will do what you want to do.
but if you want to use a IR receiver and emitter LED you may be able to alter the $50 ir upgrade but i am not sure on that as i have not had a close look at it. have a look at the $50 dollar IR upgrade and see what you can gain from reading the code.