thats very costly, because i think the whole assembly would have to be replaced (i could be wrong)...just to let u know. Anyway...speccom (specialized communications) does that i think.
I had a replacement on mine, because there is a small lib that keeps the lensbarrel from untwisting. You can sort of unscrew you're lens 'housing'. It broke when I wanted to take of my fisheye. I contacted the dutch service for panasonic, and they told me it would cost about 790,- euro's ex. VAT. (about 1140 US Dollar).
I broke it on holidays, so I was covered by insurance... But I think they have to replace the entire barrel to replace even only you're lens. It's sealed into the barrel. I will look if I have any pictures of it.