Q1: I think you might be able to fix it by increasing the buffer. CTRL + P I think gets you to preferences, if not, right click and choose preferences... Then, highlight mp3 playback in the top box, and choose configure. Then increase the buffer time. See if that helps at all.
Q2: Not exactly. Apparently there used to be one offered from kazaa, but not anymore. You could try using wine or something similar, but I have had no luck doing such yet. If you haven't heard about gnutella yet, there are several clients available for Linux using the gnutella network. Limewire and gtk-gnutella are just 2 of many.