I don't find the amount of time you are reporting too unreasonable. It took us 9 months to go live with one employee on the conversion full time and 15-20 others part time. We were using what was then Wind2 FMS and found our processes to be the hold up - not the conversion of data. Other members of our local users group have taken similar amounts of time, and one firm took at least 2 years. It seems to be a lot like painting a room. The amount of prep work you do can make or break your implementation.
We have been live for over 3 years and we insist that our 80+ Project Managers create their own project records. Each project is then examined by Admin staff to make sure it conforms to our standards. (Yes, we use work flow to do much of that tolerance checking, but you just can't replace the human eye.) We have the potential for many hands to be working on the same data records at the same time, but that doesn't seem to be a much of an issue for us.
We are currently running Vision 5.1. The area with the most sensitivity to data corruption-type problems is Project Planning and we have had problems with multiple users in a single plan at the same time with negative results. In Vision 6.1, Deltek has created an Option to 'Check out' a Plan and keep conflicts from happening. Since we are only in a test mode, I can't report on what happens when my Project Managers try to really use it, but it seems simple enough.
We are not using the SF330 module at this time. I found this post while looking for recommendations on how to use the Project Codes.
I would also add SilverEdge at
http://www.silveredge.com to the list of consultants to consider. I have found them to be very honest with me about what they can do, what recommendations they have regarding approach, and what the software can do. Good Luck!