PR560 payroll history

We are pressed to get our 2007 payroll history into the system and I had a few questions.

The consultants made this sound as if it was going to require extensive testing. If my upload sheet passes in report mode, I'm assuming that it will pass in update mode. I'm also assuming that the system will then take the data and properly add to the current totals in the system (though I plan to query to check)...but is this really supposed to be this complex of a project? I know that we've worked hard to get the sheets error free and was expecting that this would be the hardest part.

Any advice?

We have to upload payroll 1 - 8 as we implemented Lawson in April. Would it be recommended to upload these at different times, or should we wait until we have all 8 sheet ready and error free before uploading them (I'll upload them one at a time)...but did not think it a good idea to do them days or weeks apart.

Any Advice?

Any advice given is greatly appreciated and I hope one day to return the favor once we get this Lawson stuff under our belt.