Hartwell is best known for hybrid's and stripers and that is what most guides cater too.
Here is a link to a map of marina's. You may call some of them and get a recommendation.
http://www.lake-hartwell.com/thelake/lakemap.htm#c
Yo could also email the South Carolina Crappie Assoc. to see if they have anyone who guides on that lake.
http://www.sccrappie.com/
Also post your request on the Georgia and South Carolina boards directly with a heading Hartwell Crappie guide wanted.