Can I take someone to small claims court for money owed for 3 years now?

Yes, 2 years is well short of the statute of limitations for breach of contract. Yes again, the 20 facebook messages can be introduced into evidence to establish the existence of a contract  (  or loan  ) and the amount owed back. At the District Court level you have to telephone the Court to see the maximum jurisdictional amount. Also, you should file your  Civil Complaint in the District Court where the defendant resides or where his business is located ( if it was a loan to the business ). If a sheriffs' sale or execution is necessary, it will be easier and cheaper.