Wondering if I connect a shotgun (mono) into a GL 2 ext mic input (stereo) if things will work ok with no damage (shorting out etc). I realise that I will only get the one channel of sound......

You need some kind of adapter to route the signal to both channels. Otherwise you're likely to get interference problems. I don't think you can do any damage though. Try this:

http://www.bhphotovideo.com/bnh/controller/home?O=productlist&A=details&Q=&sku=352326&is=REG&addedTroughType=search

Double check with B&H that it routes the signal to both channels. It would be better to use a transformer balanced XLR adapter though. There's lots of options for that.

No damage worries, and I wouldn't expect any interference. But like Marco says, it's very cheap and convenient to record the mono to both channels.

If I'm only using a mono shotgun I usually just plug it straight in and only record to one channel, then when I edit I just the clip to left channel only (or whatever) in Vegas - I hate having innecessary adaptors due to more posible bad connections, and greater susceptability to hum/interference, etc

Colin,

Indeed, you won't damage your camera by plugging a stereo mic into a mono input. And unless you have a stereo mixer taking a double right/left channel feed to your camera you will only get a mono audio feed anyway.
Therefore....not an issue.

Sincerely,

Stephanie