An XLR cable used with an adapter won't give you the audio quality that an all-XLR cable will. If audio quality is really important, I'd buy or borrow an external recorder that takes XLR cables directly. If this isn't an option, pick up an XLR to 1/8" adapter cable. I suggest taping the adapter to the camcorder so it doesn't move around much.
(Mic cables do move around, particularly if you have a boom operator. However, with an interview, you may be able to use on-screen mics in stands or a single, overhead mic on a stand or hung from the ceiling.)
If you need two mics for the interview, you'll need a small mixer which you can then feed into the camera.
Wireless only really makes sense if you want to use lavalier mics on the actors; wireless systems introduce additional complexities, as they're less plug-and-play than a standard cabled mic.
Balanced versus unbalanced audio:
Any signal chain will have line noise. An unbalanced system (like an XLR cable going into an 1/8" stereo adapter would be) will have more of it. XLR cables (with three connectors) are good because they deliver balanced audio, which is another way of saying that they can do long cable runs without much noise.
A 1/8" cable has also three connectors, but usually because they carry a stereo signal, which is not the same as an unbalanced one. I assume the stereo cable jack on your camera means that the cable run is not balanced - repurposing that third prong from ground to a stereo signal is what does it.
Although I think it's technically possible to have a balanced 1/8" jack, I've never heard of one. (A stereo signal carried through XLR would neccesitate two XLR cables.)
According to Panasonic's specs, your camera uses a "stereo mini" jack, not a balanced or TRS jack. Connector quality would be even more important in that case, since you're feeding an unbalanced analog signal to the camera.
If you have a little time, perhaps getting two adapters - one high-end and one inexpensive - and doing a test may be in order.
Conclusion:
In your situation, if buying or renting an external recorder isn't an option (around $300US), a good microphone feeding into an XLR to 1/8" adapter will introduce line noise, but will also give you getter audio quality than most onboard camera mics.
