I agree with all the replies thus far and one thing you definitely need to do is ...
1. THROW OUT ANYTHING that dealer has told you so far since he/she is smoking some BAD STUFF.
2. Find another dealer that is competent for any future service/advice since the one you have now is INCOMPETENT bordering on being downright DANGEROUS.
3. Assume that whatever that dealer does to set up your hitch system will be DONE WRONG so either take it IMMEDIATELY to a competent dealer or redo the setup sooner than later and I would recommend you become familiar with the setup procedures for whatever will be installed on your trailer and then PERSONALLY watch it being installed to assess just how bad they are going to SCREW IT UP.
Good call on going with the Equal-i-zer and make sure you get a properly sized one with sufficient capacity to cover potential tongue wt. that might apply.
Larry