Need help quick

[OneBadH2]

I am new to Hummers and I just got one 3 months for a graduation present from my parents. Yesterday I decided to change my oil because I needed to save some money. I'm sure you all know how much gas these things suck down. Anyway, I pulled the plug and drained out all the oil. I have one of those oil filters with the magnet on it so I didn't need to change the filter. Anyway, I went to fill the oil back up and it only took a qrt before it said full. I also found it strange that the oil I put in was a brownish color and the oil I took out was red. Anyway, I headed to a friends house last night and I start to get this grinding noise. I have no idea what it could have been. I was doing about 75 at the time so I immediately pulled over. I checked it over and saw no problems. I start down a side road and get more grinding. I do a few stop and go's to see if for some reason it was the brakes. I drove it to the Hummer dealership today for them to look at it. I hope they find the problem and get it fixed real quick. Any ideas what could have gone wrong?