92 Camry, will install disable central locking

Will I have to disable or loose the factory central locking system if I install an alarm (or keyless entry) and set it up so that it has the progressive (2-stage) door unlock? Background: I want to add Keyless Entry to my 92 Camry which has factory electric door locks. The factory set up is so that when I use the key to unlock the passenger side door it unlocks all the doors. However, when I use the key to unlock from the drivers door I have the option to turn the key clockwise to unlock only the drivers door, or turn key counter clockwise to unlock all of the doors. I am used to this and enjoy having these features. If I install a keyless entry, it appears that a basic installation will lock and unlock all doors simultaneously when using the FOB. I believe this installation would still maintain my original central locking features when using the key because no wires are cut. Would that be correct?   Nevertheless, I would prefer having the progressive door unlock (i.e. push once for drivers door and push twice (or another button) to unlock all doors.) From research and reading of the forum here, it appears that in order to get the progressive door unlock working on the old Toyota's, I will have to find the wire that shows 12V+ when you hit unlock and cut it. When the correct wire is cut, I believe the drivers door will stop locking and unlocking but the rest will still work fine. I've also read that once you cut the correct wire, you can verify that unlocking the driver's door by hand does NOT cause the other three to follow. Assuming I find that 12V+ wire and make the cut and complete the installation for the progressive unlock; will that mean I would then loose the ability to use my key in the drivers door to unlock either that one, or all of the doors as it is now? Also, if there might be another path to get progressive unlocking while maintaining the original factory locking system please point me in that direction - - or if I'm making it more complicated than it is please let me know.