First, to register custom development, I will refer you to look at doc. ID Note: 133995.1 at metalink if you have access or otherwise I can send it to your email address.
Your second question is not quite understood, but you don't have to do anything on the database side. If your custom application whether forms, or report or SQL/PLSQL is executing well, all you need to do is register properly in the Oracle Application.
And thirdly, here are list of good 11i books:
1. Oracle E-Business Suite Financials administration by Shankaran Iyer
2. Oracle E-Business Suite Manufacturing & Supply Chain Management by Bastin Gerald, Nigel King, and Dan Natchek
3. Oracle E-Business Suite Financials Handbook by David James, Graham Sebiert, and Simon Russel
These books can be purchased at the following places:
Oracle store, Oreilly, Amazon websites