To be honest, I think 8x10 is even easier than smaller plates. I learned by doing whole plates, but then went smaller. For a long time I did only quarter and half plates. If you feel more comfortable and econimic with smller plates, you can always use inserts.
if you want to start small, it is pretty easy to modify a fidelity holder by having a machine shop cut 1/4 plate hole in the septum. Then use epoxy to glue small, acrylic or aluminum corners and you're pretty much ready to go. You'll need to cut a backing glass plate to size if you are doing aluminum plates. If glass, all you need is a spring to give tension on the plate. I use a strip of bowed scrap trophy aluminum.
As for chemical run-off and mess, there is always some. But if you keep your workflow clean, dry off the back of the plates after treatment in the silver nitrate bath and keep the holder wiped out between each plate, you can minimize the mess and anything on your camera. I use a LOT of paper towel when I work to keep it clean and dry, but beware that as much as you try, something will get somewhere. It is the nature of the process.
It is possible to teach yourself, but very beneficial to work with someone your first time. It cuts out a lot of trial and error. It also gives you insight into how the chemicals are handled safely. This takes away a lot of the intimidation. I also found that Coffer's DVD's were very helpful. By the time I went out to work with Kerik, I had a pretty good knowledge of th process, but had just never poured a plate. When I got working at it for real with K, it was pretty easy. I came home and went solo right away. Had I gone it alone, it would have taken me much longer.
Hope this all helps!