The OAG wont work with your newt, as it is a canon 40d has if that 5mm back focus to spare. the other thing that some ar'nt mentioning, is that a OAG+guide cam is going to weigh your focuser down. so what was going to be a OAG+guide cam will turn into a 3-500 dollar focuser as well.
I know for a fact that the SW focuser isn't really good enough for holding a 500g DSLR let alone anything else.
For the 10" use a 80mm ED refractor that doubles as a wide field. for the ED put a finder guider on it and it will be brilliant!
If you defiantly want to head down the OAG then you'll have to do some decent modifications to your newt to get A. the in focus, B. Stability of focuser increase to a minimum of 2.5" if not 3" focuser which leads to. C. increase the size of your secondary to accommodate for the mirror moving up the tube. It can be done but you have to think about a few things first.
Currently im working towards OAG, but I will most likely just hit AO straight up, as starlight does a great little set up for it. Its not cheap, but there's definite benefits to it. Hope that gives you a bit of a understanding.
