Getting the Right Request for the Systems On-Hand?

Techmaniac asks: "As a newly minted employee at [insert org name] I have been tasked with creating an RFP to secure a vendor for helpdesk/sysadmin services. Currently, we have a single individual that does all the relevant tasks for a small organization of less than 100 people. My boss has explained that the needs are for onsite helpdesk, backend support, systems admin but that she doesn't know what or how much the current person does on any given day. Having done (using the term loosely) some of this work for a smaller org, it is possible for me to create an RFP for the company. I have been here such a short time that I wouldn't want to miss any of the important tasks, nor would it set my tenure off to a rousing start. Has anyone else been in this situation? Do you have any insight into the mandatory RFP inclusions for a vendor provided sysadmin, helpdesk work? Is it within this document to dictate how many people should be onsite for the task and what can be accomplished remotely?"