First, if its a standard kernel patch driver for the Nvidia, you may have to recompile each new kernel, depending. I've had vid drivers that crossover, and vid drivers that need to be compiled into the kernel each time.

Secondly, leave the old kernels in grub until you have booted intot he new kernel once or twice to make sure it doesnt conflict in any way with your system. Until you test a new kernel its good to keep the old kernel on the bootlist as a backup, in case something should go wrong.