Hi smoovie,
I'll let one of the equipment/piping folks answer your leak questions, but the bubbling noise you hear probably is just air that is getting into your system somewhere, which is why you see air bubbles coming from the jets. One of the most common places for air leaks is the strainer basket lid--do you have that tightened down really well?
I doubt you'll need to replace the sand--there's really never any reason to unless you have been through a Baquacil conversion or used something in the pool that really gunked it up, however, it's possible that you may need to "top it off", if you've lost any through backwash.
Bookmarks