Ok here's what I'd suggest, If you already have a camcorder use it if not go out and buy the best video camera you can. Don't buy a dvd camcorder. They are designed for consumers and thus aren't very good quality. Since you want instant dvds out I would suggest getting an external box like this lite-on one for $209
http://www.circuitcity.com/detail.jsp?oid=93185&WT.mc_n=67&c=1&b=g&u=c&WT.mc_t=U then just run an s-video cable, will have higher quality than composite and a stereo pair of rca into the back of the dvd recorder hit record when you want to start and stop when you are done. In addition, you can record onto the camcorders built in dv deck as well giving you a backup of your interviews as well. In addition, you can have interviews as long as 2 hours still fit on one disc using this method while still retaining very high quality. Let me know what you end up doing hope this helps.