For References: You should have for references from the manager in which you have done the most work for and has complimented you on something that you accomplished that was a plus for the company and made the company look good. If that manager say yes, then you politely ask him/her for a reference letter in case the interviewers want to have it in writing. It is always a good idea to have a couple of reference letters to bring to your interview. If you want you could ask another manage for one also especially if you did different jobs for the second manager. That way when you give the reference letters to the interviewer, that interviewer gets an all around look at the skill that you have.
References are important to have, but not all companies ask for them. It is also very important that you leave this company on good terms so that if they are call about you the report will be good and they will say all the nice things about you.
I wish you the best!! and if you have any other questions on this or other items please let me know!!