|//dpfwiw.com/ir.htm is a good place to find info. From what I've read, the G3 doesn't take good IR, although I can't recall why.
Mind you, I read that the G2 doesn't, either, and I've taken some outstanding IR shots, using a Hoya R72 screw on filter. My Pro1 takes pretty woeful IR shots though, compared to the G2. Obviously some cams do it better than most.
Would be worthwhile checking the filter out, and asking if you can borrow one, or pay for it and take it back if it won't give you a decent shot.