Instructions on how to download the MPL RS5K scripts:
In the ReaPack menu, hit Synchronize packages to make sure you've got the most recent default repositories. Then go back into the ReaPack submenu, this time hit browse packages. You'll land in a search field, type in RS5K and hit DownArrow to jump to the search results. Move down to RS5K Tools by mpl, hit Tab to get to the Actions button, Space on that to pop up the context menu, and choose install.
Go back to the search field, this time type various functions. DownArrow again to the search results and you should find a package called various functions also from mpl. This time, you need to install a specific version (the most recent free release), so in the Actions context menu, go to the Versions submenu and check 1.31. Hit the Actions button once more and check "Pin current version" to make sure ReaPack doesn't update to a newer version when you synchronize packages in future.
Once you've done all that, hit OK and ReaPack will download the goodies. Now if you search for RS5K in your actions list, you'll find a bunch of scripts to speed up loading samples.