So long as your multisamples actually exist in either Rapture Pro's or Dimension/Rapture 1's multisample folders, everything should load correctly without any need to do anything special. Alex had the unusual case of an incorrect imported value, but that's likely due to something from a previous SONAR/Rapture 1 install on his system.
I'll use Alex's Steinberger Bass pack case as an example of how a typical scenario goes. User has Rapture 1.2.2 installed, multisamples installed to either C: or an external drive (the behavior as far as Rapture Pro is concerned will be identical). They've installed their Steinberger pack, and this loads and plays correctly in Rapture 1.2.2.
Next, they install Rapture Pro. Again, the exact location of where they choose to put their Sample Data directory doesn't matter, but for the sake of argument, let's say D:\Cakewalk Content\Cakewalk Sample Data. Rapture Pro then completes the rest of the installation, and as part of this, copies the existing Rapture 1.2.2 programs into Rapture Pro's own programs folder.
Now you open your host, and insert Rapture Pro. With Update 1, you'll notice Rapture 1's programs now have the lovely new custom bank art (and the bank selection brackets). You go to the Steinberger Type, click to load one of the programs, and now that Rapture Pro has your correct legacy multisample paths, will grab those multisamples directly from their original location, and everything loads and plays correctly.
Hopefully this helps make things a little clearer (especially for the non-technical types). Thanks guys.