The scene where he is in the hospital shows actual outside footage of the then-130th Station Hospital in Heidelberg (actually Rohrbach then, in a former German signal base), where he was treated and died, without the more modern clinic building that would be in the way of the shot today. There is a plaque in the hospital beside the door of the room he died in.
Jean Gordon (portrayed by Kathryn Leigh Scott in the film) was General Patton's niece and it was rumored over the years that they may or may not have had an affair. Some claimed Patton started the rumor as he was getting on in age and was trying to maintain some vestige of his manhood and that the relationship was more like father/daughter. Gordon was also said to be romantically involved with a married U.S. Army officer while in Europe in 1944-45 and was despondent when he left her to go back to his wife. Others state that the affair did in fact happen, and she was confronted by Beatrice Patton about it a few weeks after the General's death in December 1945. Sadly, either way, Jean Gordon took her own life by leaving the gas stove on in her apartment in January, 1946.
Although, in this movie, it would look like the accident that General Patton was in happened the day after his birthday (The soldiers in the truck are singing one of the tunes played at the generals birthday party), the accident happened on Decenber 8th...Almost a month after General Patton's birthday.