Hi tirediron - good video images in low light and a long zoom are the easier part - "good audio quality" is a little tougher. There are a couple of prosumer interchangeable lens cameras that can do this job, but they aren't reflex-mirror DSLRs.
There is
one "DSLR-type" interchangeable lens camera in your price range that can record for 2 hours with no overheating - and has adjustable audio level control: the $649 Panasonic GH2. With the Panasonic's 2x crop, a used Olympus 50-200mm f2.8-3.5 lens for about $650 and a $100 adapter, you would have a very capable low light camera with pretty long reach (it has a consumer 2.5mm mic jack, so it needs a $5 3.5mm to 2.5mm adapter to use standard consumer mics ). I own this camera, and it is the best-value-for- money large sensor, interchangeable lens video/still camera out there.
Here is what it can do in a choral setting (from GH2 shooter Arlene DiJulio - please watch in 1080p):
https://www.youtube.com/watch?v=FaMERjpTBWM
The other interchangeable lens option is an interchangeable lens camcorder, the Sony NEX VG10, which is available used for as low as $1290 at Amazon. This large sensor camcorder is very good in low light, even with the slow kit lens. I have shot with its younger brother, the VG20 ($1100 body-only), so I can vouch for its low light performance.
Here is what the VG10 can do in a choral setting (please watch in 1080p):
https://www.youtube.com/watch?v=DS5c48nKf0E
If your friend doesn't want to bother with interchangeable lenses, my recommendation for this job would be the small sensor $1100 Canon HF G10 camcorder. It is the low light champ amongst fixed lens prosumer camcorders, and has decent audio (with a consumer 3.5mm mic jack).
The pro version of the HF G10, the Canon XA10 with professional XLR mic inputs, is above your budget - but if you are willing to look at an older pro model such as a used Panasonic HMC40 for $1260 and a used XLR adapter for $225 , your friend might be able to have his or her cake and eat it too
Hope this is helpful,
Bill