Hey Pete
I am so sorry to hear about your misfortune and truly hope you catch who did this. In my real job I actually install security cameras and I hate to tell you but what you have recorded is what you are going to end up with. Despite what these ridiculous CSI shows lead us to believe the ability to enhance picture, add colour, increase pixels, sharpen up the image etc etc etc is total crap. The ability to enhance recoded video is almost totally negligible especially if we are talking older style analog cameras (think increasing the resolution on your old CRT TV) I would offer some solutions to combat this happening again in the future. Were the cams inside the shop/barn? If so if I would suggest leaving a light on so the cameras have the necessary light to pic up an image, if not then you can explore having the lights triggered by a motion detector. Detector trips lights turn on and camera gets a picture or the easiest, cheapest and most low tech method install one of the porch lights with the built in motions on them inside the building and when tripped by someone entering just like someone walking into your backyard the light turns on and the cam will be able to pic up a much better image. There are obviously higher tech solutions involving light finding cameras, IR boosters etc but I would think mostly price prohibitive for residential homes. Again. I am very sorry for your loss.