You can get an Agent to negotiate with the FSBO seller, but if they can't get the seller to pay their commission, you may have to. Make if clear up front as to how much the agent will get and who will pay him/her.
Once you have agreed on a price -immediately go to an attorney or agent who'll write up the deal, then get everyone's signature. The deal must close 30 days later after you get financing, the seller clears the title, etc…
What to do to close the deal
Open escrow
Get financing (exclusively the buyer's responsibility)
Clear the title (exclusively the seller's responsibility)
Get a professional home inspection
Read inspection report and negotiate repairs
Get termite and pest report
Pay for repairs to get a clearance (usually the seller's responsibility)
Prepare disclosure statement (seller)
Read and Accept/Reject disclosures (buyer -take them to a good agent to learn if all state and gederal disclosure laws have been met)
Negotiate repairs or discount based on inspections and disclosures
Get title insurance for both you and, if needed, the lender.
Arrange a final walk through (to be sure the seller has't damaged the property during the escrow process)
Make sure the seller moves out on time
Get key
Move in