Bad tire after 160 mi

I was washing the truck yesterday and when I got to the tires I noticed a rip in the side wall at the tread line. Went to the dealership and they replaced it. They nor I could determine what the cause or defect was. I should have taken a picture of it :o

I believe one of my tires is bad, because I am getting a right pull on and off. It comes at high speeds and mid-range speeds...I haven't noticed it so much starting off or taking off from a light, or stop sign. It's also not something that is happening during hard acceleration, but rather any time.

P.S. Did they just replace one wheel or both front, etc? How much hassle did they give you?