It is perfectly normal to be nervous the first time(s) Be sure to tell your Instructor of your apprehension and (s)he (should) go over the procedures and explain the aerodynamics of a stall while on the ground. I normally set aside .75 hr ground instruction for this subject before we ever do it in the air.
Remember, You cannot spin unless you are uncoordinated. In the 172, you would just about have to input full rudder deflection to get it to spin. The Cherokee I fly, is very hard to get it to FULLY stall and spinning it on purpose takes work. The 172 is very stable and will want to recover on its own given enough altitude, as you would not have do do anything but keep it from yawing with the rudder to get it to recover
It is normal for someone that has not stalled the plane to be afraid,mostly because of the OWT's. Take my word for it, it is not as bad as you envision. 95% of my students say after their first stall(s) (just like most after a roller coaster ride) . "that was fun, lets do it again!".
The main purpose of stall training is so that you can recognize the onset of a stall and prevent it from doing so. Often, all that is needed is to lower the nose (angle of attack)
Although spin training is no longer required by the FAA, I demonstrate (to be legal with out parachutes, "it is their first CFI lesson") a three turn spin in both directions to my students so they will see that there is no need to be terrified and recovery is just a matter of following the correct procedure. Spin recovery in a 172 is very easy (and as I mentioned before) it is very stable and will "want" to correct it itself.