Make certain your software will allow for audio and video. I use Multimedia Fusion, it’s a bit fussy but very versatile.
You have a pretty tall order for what you want to do. I recommend looking at used, standard-definition camcorders.
SInce you’re on a budget, I also recommend choosing a location with great acoustic properties. This way the microphone won’t be as important.
As for software, I can vouch for Adobe Premiere 6.5 and up. You can get free trial software from adobe.com
I used to create aircraft maintenance CBTs, so I’ve had some experience. Good luck!