Business Scenario for RFP

What information do you need based on the business scenario to write an RFP (you are not required to actually write an RFP; however, you must have gathered enough information from this discussion to create)? 
Business Background The business is a county office providing county services to a population of approx 200K citizens. Services include road maintenance, health services, assessor, treasurer, courthouse, counsel, etc. There are approximately 1,200 employees ranging from office workers, to road maintenance crews, to mental health workers, to corrections officers. This office is in a more rural area, however, has very little HRIS systems currently installed. They have been benchmarking against other county offices and found that there are a variety of technologies that might help them manage the employee staff. 
The county currently has no official process for conducting performance evaluations other than an employee should receive one 3 months after being hired and then annually thereafter. There is currently an exit interview form used, however, the information gathered is useless and often times those separating do not even complete or are even given an exit interview form. 
This county HR office uses Windows based software. Compatibility is not an issue at this point so no need to address the technical aspects for purposes of this RFP.