LCD vs. no LCD will make a BIG difference. But every camera model has it's own run rate, so you'll definitely get a better feel with experience. It's hard to say what battery life you'll get unless someone has the same model camera and the same battery.
Also, have you tried to run line-out from the DAT to the camera before? Not sure about that specific camera, but most consumer cams expect mic-in levels not line in. One simple (albiet less-than-ideal) workaround is to get a cheesy mini attenuater from Rat Shack -- they are sold as a "headphone volume control" usually, they have a female mini on one side and a male mini on the other, with a volume dial in the middle. Not ideal for quality to stick it inbetween, but if the DAT is sending line-level signal and the camera is expecting mic-level, it'll work, and it only costs $10 or so. There are other better options such as XLR-to-Mini adapter boxes that screw into the bottom of consumer cams (most have an AUX mini in with a line/mic switch too), but they're more expensive. Also, another thing to watch out for in your videocam is if you have control over the audio, make sure to turn AUTO GAIN CONTROL OFF!!! And if you can manually adjust the levels of the cam, turn them all the way down to near nil, and then only attenuate the incoming signal as much as you need to get decent levels -- this minimizes the camera's POS preamps in the gain staging.
EDIT: Doh! Another approach is to go out the DAT's heaphone jack and adjust the headphone volume accordingly...