1640 has a great website dedicated to their work with swerve over the years
http://wiki.team1640.com/index.php?title=Swerve_Central
When we designed our swerve last summer their team was an invaluable resource. Chief Delphi is also a great resource, there are dozens if not hundreds of threads about swerve design, pictures, and models of what others have done or thought of. Just search for "swerve" or "crab"
How much did your mecanum drive weigh? 1640 has modules that weigh around 8lb, MOE was able to trim it down to 7.2lb (lightest in MAR that I am aware of), AndyMark sells an assembled module that comes in at 8.2lb so keep these numbers in mind and decide if a 30-40lb drive is worth what swerve can do for you.
Also keep in mind I would say at least 70% of the work is programming after you have a working set of modules, be prepared to leave time for your programmers to play with it after it's up and running. We are still making programing improvements and will probably spend this summer working on even more.