Converting to referenced won't affect your versions at all. To convert use File>Relocate Masters, then define the folder structure you want to use, you can do just a few to start to see how it works, it's not an all-or-nothing deal, you can have a mixed managed and referened library.
Once converted you shouldn't notice any difference to Aperture. Remember, a version is just a set of instructions that is applied to the master when needed to generate the modified image, it is in the library and takes up very little space. The previews and thumbnails do take up space which is why referenced libraries aren't as small as people expect.
People generally see performance improvements when converting to referenced, though it would be better if the referenced images were on a different drive to your library.
Other things will also really help performance, make sure your hard drive isn't too full <70% ideally, max out your RAM (Aperture is heavy on RAM) If it's an old MBP try running in 32-bit mode. On my old iMAc I use an app that frees up unused memory and this also helps.
Have a look through this forum, the topic is covered a lot. You aren't alone with slow Aperture, I do feel you are more lonely needing to access the master images.
HTH