http://www.teamxray.com/teamxray/sho...p?file_id=4461
If that doesn't work google 'hudy setup guide manual'
Download the file and you'll have 40 pages of everything you could want to know.... This is not a bible however just a reference... Does every driver agree on what is said, no, but the changes stated in there give you something to look for once you make the change.
For center diff front or rear weight bias all that has to do with is giving the rear tires less or more traction.
For shocks vs diff oils, I treat them completely separate from one another. Yes the front diff oil will effect turn in, turn out, and on-of power steering. However the shocks need to be tuned to handle the track first and give you consistent lap times, then the diffs can be tuned to bring those consistent lap times down. Being a weekend warrior racer you really should focus on shocks, find the diffs that you're comfortable with and stick with them. When you start going crazy with racing then the diffs will be a tuning tool to run with the best. You can win the world championship running 5-7-3 for diff oil.... running bad shocks..... not so much.