That was clear enough, cause "I want to uninstall kp48 and install kp49, what to do?" seemed to strange question for a person with average experience (rest of Your post seemed so). Again, no mocking up.

You just need to uninstal (apt-get, button in menu, FAPMAN, whatever) kp48 multiboot, kp48 modules and flasher (it's not needed). Then, just install kp49bootimg from repositories (it will pull modules automatically). If, for some reason, your kp48 installation was screwed and You can't auto-uninstall it, extract packages that You installed, and check where file land, then delete them. don't forget about multiboot entry, too.

zImage is in /boot/multiboot.d/ - for modules, it's better to uninstall them automatically, or follow method I described in this post.

/Estel