You get an OINP request after you create a EE (Express Entry) profile. If you successfully get a OINP nomination you can boost your total by 600 points such that you are able to get an ITA (Invitation to apply). So yes, you can do both.
yes, but i think OINP needs some number of years minimum as work experience... i heard it was 3 or 5, but i cant be sure... someone will have to correct me.