Moving contacts from Outlook PST to Exchange

[DaveM]

I'm presently using Outlook for POP e-mail and contacts, syncing the contacts to my iPhone 5s through iTunes (not iCloud). I'm going to be adding a hosted Exchange e-mail account in Outlook and want to move my contacts to the Exchange account there. I have not yet set this up. A couple of questions, please.

Can I use the Import function in Outlook to bring the contacts from my present PST to the Exchange account? If not, how do I do it?

Obviously I'll have to stop syncing the old PST contacts with my phone, but once that's done, how do I tell the phone to use the Exchange contacts instead of the ones from the PST?

Is there anything else that I should know and be careful about in making this transition?

Thanks!