Two things I noticed:
"Oh, yes you're!" Should be "Oh, yes you are." Ending a sentence with a contraction is a little awkward. I'm, you're, he's, etc... usually goes at the beginning of a thought.
You're going to be out of town next week, right?
Yes, I am, but only for one day.
However you could also respond with:
I'm going to be gone, but just for a day.
The other thing, which is minor, "too much of heroin"-- the of is unnecessary. "Too much heroin" is the correct phrasing.
Otherwise, good sentence structure and idea expression.