What's the distance between where you want to mount the cameras and your door and the fuel tanks? That'll help decide lens length (the zoom).

 Personally, I'd look for a place as close as possible to the door and the tanks to mount both that has wired access to your network if at all possible. Powerline network adapters are sometimes really handy for getting 'net to outbuildings if they're wired from the same panel as the main building (shop or house).

 As far as cameras go, that depends on budget, but don't expect miracles from cheap cameras, particularly cheap analog cameras. I've tried a fair number of cameras from cheap analogs to $1000 megapixel high definition Axis network cameras, and from what I've seen the best bang for the buck is a bit under $200/camera with Hikvision hidef network IP cams (or a rebranded Hikvision like Swann and Lorex). You get a 2 or 3 megapixel high definition picture that'll give you MUCH better detail than any budget analog cam from a kit. The 3mp mini bullets are excellent bang for the buck, especially if you need a 12mm lens version for distance shots. Lots of cams around with 2.8mm wideangle lenses, 4mm, maybe 6mm, but budget 12mm cams for distance shots in a shop yard are harder to come by. They'll read a plate from a moving vehicle in the daytime at over 80'.

Here's a link to a review of them. http://www.networkcameracritic.com/?p=1791

The site has tons of reviews with sample pictures and video from a lot of other network cameras as well.