2003 Buick Rendezvous Oil & Coolant Leak

Engine problem
2003 Buick Rendezvous Engine Size unknown All Wheel Drive Automatic 102000 miles

I noticed at the start of December that my car was getting hotter than usual on a long drive, just over the half way mark, and checked the coolant level. The coolant reservoir was low, so we added the recommended dex-cool coolant and continued on with no more issues. After driving the car another 2,000 I added more coolant to the reservoir. There is a little bit of leakage on the floor of my garage (about the size of a quarter a day), but it looks dark and more like oil than coolant. I had the oil changed in mid-December. I have been checking the level of the oil and transmission fluid and they are just fine. The car seams to be getting hotter than normal when idling, but never more than half way to hot. Other than that I have no issues, the drive drives really smooth and sounds quite. I have seen a lot of posts about issues with the intake manifold on the Buick cars, could that be my problem? If so any estimate on repair cost?