If I have a criminal background from when I was younger, would it affect me now that I want to become a US citizen?

The immigration consequences of criminal matters is among the most complex topics in immigration law. There really is no substitute for you to obtain court-certified copies of full sets of disposition documents for each criminal arrest (or to obtain appropriate letters from court clerks explaining why no such records still exist) and to consult with an immigration attorney who, after learning all of the relevant information, could advise about naturalization eligibility, and who then could offer legal representation in the often complex application process.