I have a few different file types of sounds I wanna use from third party sources, but I'm having trouble loading them into my sonar professional. They are fxp, from Nexus. Also, how do i import Wave files into my piano roll, i have alot of 808 sounds but can't use them without transposing each individual hit.

Hi. To use .fxp (Nexus extension), I believe that you need Nexus. Piano Roll View (PRV) is MIDI only. The 808 sounds could be used (depending on format) in a sampler (Dropzone, JUST to mention an included one).
Hope this helps.
All the best.