Rothermel is right the Licensed Battlefield Guides are not allowed to drive you around the field in your car. In the interest of full disclosure, the National Park Service has forbidden to use of even hands free phones between stops. Nevertheless, we are still giving effective tours. You would follow the guide in your own car, and make several stops where the guide will explain what happened at that location and also answer your questions. The cost for a 3 hour tour booked directly with the guide association is $94.50 for up to 6 persons. I recommend that you call ahead to 717-337-1709. You will hit a voice mail. Leave your name, phone number and the date and time that you want a tour. You will get a call back, usually by the next evening, from the guide who is assigned to your tour. The guide will work with you as to where and when to meet, and also want to know what special interests you may have if any. If you tell the guide where you grew up, he or she can show you areas where men from your home county fought (assuming there were men here from your county). As you can tell by my moniker, I am one of the LBG's, so yes I am a little prejudice. Having said that, the guides, who have been licensed through a rigorous testing process, do a rather good job. Check our reviews on the internet.
I would second the motion that you see the museum in the Lutheran Seminary building, and also the Shriver House on Baltimore Street. The latter does a nice job of giving the view from the civilian side. Do not miss the Cyclorama painting at the Visitor's Center. The Cyclorama is a 360 painting depicting the high water mark of Pickett's Charge. It was created in the 19th Century, and some Civil War veterans who viewed it are reported to have said that it was an authentic depiction of Civil War combat. The Visitor's Center has been closed on Tuesdays and Wednesdays of late. Check the website for the Gettysburg Foundation to see if that is still the schedule and plan accordingly.
You and your wife may like to see the Women's Memorial in the Evergreen Cemetery. It is just to the left after you pass through the cemetery's arched, brick entrance. It is a statue of Elizabeth Thorn. She was the wife of the cemetery's grounds keeper, who was off to war. She will personally bury about 100 Union soldiers in the Evergreen Cemetery before the National Cemetery was organized, and she was 6 months pregnant doing so in the summer heat.