You mention you shoot a fair amount of video, I have a problem and it is only being able to shot video using the LCD screen which in sunlight is useless, it there a way to use the viewfinder or am I going to have to buy a special hood device to mount over the LCD screen? Any comments would be greatly appreciated...
You can try and turn the LCD screen brightness up and pull out the articulating screen and rotate it so the sun glare is minimized first.
But yes a viewfinder loupe is an asset. There are a number available. I use a Genus loupe on my D300s. It is inexpensive compared to others and works very well. BUT it affixes via a thin plastic frame that adheres to the LCD viewfinder cover. On the D300s that works great but if such an attachment was used on the D5100 you would no longer be able to turn the screen in to the body. And as there is no LCD screen cover you'd be sticking it right on to the camera - I don;t like the sound of that.
So a different (more expensive) style of mount would be required. But all loupes I believe essentially make the articulation of the screen redundant so I would work with that first before going for a loupe.
RRoger uses the D5100 for video a lot, I'm sure he'll chip in.
The SanDisk 32mb/s is fast enough. The only advantage of the 45mb/s is upload speed to your computer. You will need a fast card reader.
I had to modify a CaVision magnifying loupe for use with my D7000, but it fits perfectly on the D5100. Just reverse the LCD till it faces back and screw the mount into the TriPod hole. Then you will have the equivalent to a 6" viewfinder. The numbers are: MFRC2550 for the loupe and: RPMD90R for the swing away mount.