1) http://blogs.msdn.com/bartd/archive/2006/09/09/Deadlock-Troubleshooting_2C00_-Part-1.aspx. Note there are 2 additional parts to this blog series.

2) With such a complex construct (2000 line sproc, trigger(s) in play, etc) you may be best served by getting a professional on board to assist you. You could spend days going back and forth on this forum or wind up with a solution that causes other problems.