The SONAR manual would be a nice place to start. That gives you an idea of what can be done, where to look for what etc. You get the picture, then you can concentrate on one bit at a time using videos or whatever you prefer.
The tutorials you have in SONAR (press F1) give a good support there as well.
SONAR PE 8.5.3, Asus P5B, 2,4 Ghz Dual Core, 4 Gb RAM, GF 7300, EMU 1820, Bluetube Pre - Kontakt4, Ozone, Addictive Drums, PSP Mixpack2, Melda Creative Pack, Melodyne Plugin etc.
The benefit of being a middle aged amateur is the low number of years of frustration ahead of you.