I'll try to make it easy.
Call reservations and they should be able to do a name correction as long as all of the flights on the itinerary are UA. If not at the very least the TSA secure flight information can be input with the correct spelling of the name. If it is a simple mix up of the letters but you can still make out the name then not to worry as domestic travel is not as strict as international travel. Please be patient as call volumes to the reservations center has been overwhelming since the systems merger last week.
Fly by Night and Day
3 Decades of Experience working for United Airlines!
I would suggest a drive out to the United ticket counter at the airport. You need to have the ticket corrected as soon as possible to avoid any future problems.