Alfredo:
While I have no real experience with Logic Pro, I do have much experience and advice for those who upgrade from Snow Leopard to Mavericks and some "theoretical" advice about Logic Pro 8.
INITIAL ADVICE:
Backup or clone your Snow Leopard environment before upgrading to Mavericks.
DO NOT install Mavericks over Snow Leopard, as it will destroy your Snow Leopard Environment.
In theory, Logic Pro 8 will run in Mavericks, but with two problems:
1) The installer application will not work and claim to be a "rosetta/powerpc" problem, but it really appears to be a "bug" in the installer application that arises in Lion, Mt. Lion and Mavericks.
The solution to this problem should be to partition your hard drive or add an external drive and install Snow Leopard again to this new partition. Then install Logic Pro 8 and all of your loops and prior data and then upgrade to Mavericks.
2) The second problem is that I have read reports on this forum (and you can search to find them) that Mavericks causes visual "noise" to be apparent on your sound files' time line, rendering it impossible to work with.
If that is truly the case, then my advise would be (in lieu of my advice above): Partition or add an external drive and install Mavericks on that new partition. Use the "dual-boot" method (System Preferences:Startup Disk) to determine which flavor of OS X you boot into, Snow Leopard or Mavericks.
Then you can boot into Snow Leopard as you need to access older Logic Pro 8 files and Mavericks as you need to work with Logic Pro X.
In theory, you can follow both of my advised plans, so that you would have Logic Pro 8 and loops in both partitions, in the event that someone finds a "fix" for Logic Pro 8 to work in Mavericks. Use Logic Pro 8 in Snow Leopard until such time as the "fix" is found, but have already installed it into the "new" Snow Leopard which is then upgraded to Mavericks if and when the "fix" is found.
If you follow this approach, I would recommend that a third partition be established for the clean installation of Mavericks and Logic Pro X be used there, so that there is not interaction between the two versions of this program.