Walmart drug and background screenings?

Today I was offered a job at Wal-Mart, I just went and took my drug test and they are currently running the background check. 2 months ago today I smoked a little less the a "bowls" worth of weed and that was it since. Will I pass the drug test? I was told if you are heavier it takes longer to get out of your system, I'm about 6 foot and weigh about 230. About my background, when I was 12 I was caught shoplifting and was charged with a felony but it went down to a misdemeanor because I stole largely food items to help feed me and my mom. I'm 18 now, will they look that far back or just in my adult years (which aren't long.)