Thanks for the replies. Steviej, I'm going to go to a mechanic family knows and have him look at it. I described the same thing over the phone and he said it sounds like a shifter cable/switch problem but to bring it in to make sure.
Steve, I went to the pohanka lexus in chantilly. I know of the hesitation problem and I don't really have an issue with that. It's just before I got my oil change I had five gears and now only four. When the floor shifter is in the "D" position it'll never make it to 5th/overdrive. The car acts the exact same if the shifter is in "4" or "D" and the instrument panel LED indicator stays on "4" for both cases. I just found it strange how the one hour it was in for the oil change this could occur (and I do realize they shouldn't be messing with anything else). I'm confident this didn't occur before either; it's pretty obvious driving at highway speeds that I'm missing the last gear.
The thing that has me irked more so than this problem was the fact that the dealership kept on saying it was just coincidence and never a mistake on their part (maybe a liability issue) and then gave me a ridiculous quote to replace the entire shifter assembly/labor.
Andy