There is some great advice here. I jumped in the deep end and started to learn how to take photos of DSO's with an 8" Meade sct at 2000mm and later with a focal reducer. It is certainly harder and more frustrating than starting out with shorter focal lengths, but still rewarding.
My journey has lead me to using a ccd camera (after starting out with a dslr) and I found that my level of precision (and learning curve) had to increase. The image scale is smaller with the ccd than the dslr and more likely to pick up any tracking, focus or other errors. So I find an OAG really helps. However, it's harder to find a guide star (small FOV) and I find the guide star is determining my composition more than I would like. I'm still learning and looking into improving this. A sensitive guide cam is very helpful here.
My advice is to look into what camera and FOV you are interested in now, but also if you ever up-grade. This will help in which autoguider and method will suit you best.
For FOV I love playing around with camera and scope combinations on this site:
http://www.12dstring.me.uk/fovcalc.php
There is also a new book out for astrophotography, which I'm currently reading. It covers a lot of issues to think about, including software assisted or automated focusing. It's pretty good and I found out about it from this thread:
http://www.iceinspace.com.au/forum/s...d.php?t=138681
Good luck with it all and let us know how you go.
Aaron