The Travel Agent may not be able to change it and give you the same fare that you paid for. Depending on when the ticket was issued, and the fare rules surrounding it, the travel agency may be unable to make the change and if it is a function of their reservation system, there would be no guarantee that your boarding pass wouldn't still say the same thing spelled the same way.

Do yourself a favor next time, and book your ticket directly with an airline. Travel Agencies are great for travel that involves packages and hotels and things that they make money on - but asking a travel agent to work on an airline ticket is essentially asking them to work for free if they're in the US. There's a ticketing fee issued - but the agent probably isn't seeing a dime out of that in commission.