do you want your movie to be in sd or hd resolution? if it's sd, sell that old production switcher (you'll only need it if you want to operate a tv-station) and use the old professional cameras for your documentary.
if you want hd, try selling all of that old professional equipment to someone who still uses it (tv stations in countries that haven't switched to hd yet) and buy some new stuff from that and film the documentary with it.
i wouldn't want to film a whole documentary with a dslr but it's certainly possible, given the right accessoires (get at least a good tripod, external audio recording gear and some good lenses).
i assume you are familiar with the basics of photography, having a 60d. look at some documentaries you like and try to replicate their looks and the way they are done. maybe start with some short bits (say 5 minutes) to get the hang of it.
and think about where your movie will be shown before you start filming (for shooting in the right format - e.g. madagascar has been a SECAM country, so you'd probably shoot 25p with a shutter of 50 on the dslr if madagascar is your main market. 50i on professional equipment, if it's for local tv, ...)