How do I convert from aol to gmail as the primary account that sends email from my iPad?

I have been on aol forever and want to ween myself of this account and shift everything to gmail. However, I don't want to lose any critical aol emails in the short term. I also use outlook, icloud, and a fairly new dell laptop. How do I make gmail the primary account from which emails are sent from my iPad? As well as my dell laptop? Again... I don't want to lose anything coming from aol but would like all return emails to come from gmail.