that are much further from the camcorder body that the in-body mics consumer cams have but I suppose it is possible to still pick up audio from the tape drive...

What is your budget?

There are 3 ways to do what you want.

1) Rather than use the audio captured by the camcorder, use an external audio field recorder. When you edit, import the audio from the field recorder. Sync. If you need to sync lips/and spoken audio, when the echo is gone, you are sync'd. The Zoom H4 has good built-in mics and two XLR-1/4" combo jacks for external mic connectivity. Edirol, M-Audio, Marantz and Tascam make good field recorders, too. You can collect all your sound design and voice-over narration with the field recorder.

2) The GL1 has a 1/8" (3.5mm) stereo audio-in jack just under the DC power jack... in front of the tape cassette door on the side of the camera and behind the lens focus ring under the little plastic cover.

There are several decent mics that use 1/8" plugs. Sennheiser and Sony make pro-grade clip-on lavalier mics and their wireless base stations use 1/8" jacks. These portable base stations use 9 volt batteries (like the body packs).

Most other wireless mic base stations use AC power and XLR connectors - this may not be practical when you are capturing video/audio at the lake.

Lavs are best for capturing someone speaking.

3) The field XLR-adapter mixers from juicedLink or BeachTek plug into the camcorder. The XLR adapters have 2 or 4 XLR jacks. Most decent shotgun mics use XLR connectors. Most decent shotgun mics use batteries or can use phantom power - some of the XLR adapters from juicedLink or BeachTek can provide phantom power. I use a BeachTek DXA-6 and a juicedLink CX-231. The XLR adapters run on a 9-volt battery.

If the audio you plan to use is recorded to the camcorder, yes, headphones to monitor what you capture is a good idea. If you use the field recorder, then plug the headphones in the field recorder - but pay attention to the audio levels on the camcorder - when you go to manual audio, some audio meters will appear on the viewfinder.

As soon as you plug something into the 1/8" audio-in jack on the camcorder, the camcorder's "internal mics" are disabled.

A good condenser stereo mic is also handy. Audio Technica has one with XLR jacks (AT-825) and essentially the same mic with a 1/8" stereo jack (AT-822). They use batteries (and the XLR version AT 825 can use phantom power provided by the DXA-6 or the CX-231).

If you use a shotgun or other condenser mic, they usually come with a foam wind screen. You REALLY want to invest in a "zeppelin" (also called a "dead cat") like one from Rykote.