I think you would enjoy the Canon 5D. It is effectively the digital version of the EOS 3. It's got a full-sized sensor (the size of a piece of 35mm film i.e. 24x36mm) but is not "pro" only in the sense that it is not super-weather proof. If you're going to be stationed in Iraq or are shooting a lot of hard-core weather, then you'd want something really sealed. The EOS 3 isn't, so I assume the 5D will suit you just fine.
Yeah, there are some costs associated with going digital, but I think you will be pleased that you did. My "A-ha!" moment came when I was shooting inside and out, and realized I could change the ISO (known as ASA in film) with every shot. Suddenly I wasn't just "limited" to aperture and shutter speed, but if there was a shot I wanted to get indoors I didn't have to wait for the next roll, I could switch as I needed to.
What matters are your lenses, and they will work identically on the 5D.
Have fun, and stick around the forums. Every question (no matter how simple-seeming to you) will be answered with a friendly demeanor.
Have a good weekend.