Audio Set-up for Panasonic Gh2
Disclaimer - My skill level is below newbie, but I'll bump, and maybe add something of value by accident.
If you are doing interviews, wireless mics might not be the best way to go. What you could do is use a Zoom H1 or similar recorder and a lavalier microphone (which I'll assume you'll have or would use with the wireless mic).
The Zoom H1 will be the same size as the transmitter anyway, and you don't need to plug anything into the GH2. The Zoom H1 has a LCD readout for levels, a speaker to check if needed, and you can plug headphones into it directly to check levels beforehand.
The advantages being you can do the H1 + lav setup for everyone if it's a back and forth interview, while the GH2 records it's own audio via the on board microphone. You then use software like Pluraleyes to sync in post.
Of course a dry run before hand to check if it all works out would be best.
If you want to go the wireless route then maybe a SLR audio adapter (like a Beachtek) would work. You plug the receiver into the adapter, and the adapter had a headphone jack, and you plug the adapter into the camera. You will introduce the chance of reduced sound quality when you start adding things to plug things into though, on top of the wireless and tiny plugs used.
And of course multiple sources/backups would be ideal.