Quote: "So, how do I view the size, in units, of my model in Blender 2.61?"
There should be a toolbar to the right in the 3D editor. If not, just press N to bring it up. In that toolbar you should see 2 sets of options, 1 named Scale and the other Dimensions. You will want to change the dimensions of an object not the scale. The Scale Should remain at 1 for XY and Z but for static models or non animated models it can be changed with the dimensions.
Quote: "Also, what would be the optimal way to export my models, with UV maps, rigging, and animation for use in FPSC? I know I'll need to export to DirectX (.x), but I'm not sure what would be the best way to do that."
1. make sure the model or models, have no material attached to it. Just go to the material tab in the far right in the properties toolbox there. (should be the fourth from the right). When there just simply select your model then select any material in the box there and hit the "-" next to it.
2. When using bone rigs, you need to keep scale (not dimensions) at 1 on XY and Z with both the model and the bone rig. A neat trick to get the model to scale. Once you get the model the right size Duplicated and change the Scale of it to 1 on XY and Z. Go into edit mode and select all then delete the selection. select your model then select the center point of the now empty model and hit ctrl+J to join the object with the blank object to keep your dimensions while your scale remains at 1 with XY and Z. Best to do this before rigging. That way you can just edit the bone rig to the right sized model and won't have any problems with it after export.
3. everything else should export just fine.
Quote: "Lastly, in animation, would the keyframes be interpolated once exported, or do I need to do some hardcore frame-by-frame animation to achieve what I want?"
When creating animations you should only have to do the following four points of sequences; beginning, middle, end and where it doesn't look good (ex. foot goes through floor). Blender tends to fill in the blanks in between keyframes. So no real points in actually doing Frame by frame by frame by frame... animation.