This is my mess up, looking to fix it as economically as possible.

I have a reservation for the JW Marriott in New Orleans for tomorrow for 5 nights on points. I cannot stay at the hotel for that time. The cancellation policy is 3 days before. What would be the cost to cancel? I have never had this happen on points before.

However, I do need a paid reservation in New Orleans for tonight for 1 night. I have a corporate rate that would be $195. Any idea on how to ask to switch the reservations? Hotel direct? Platinum line? Could I change tomorrow's reservation to 1 night and try to have a super early check in tomorrow at 1 am? Any other advice?

I have never had a problem reducing the number of nights within the cancellation period. I would just recommend calling in.

Now in terms of your other question of changing points to a rate, I've never done that before. I would assume you may not be able to fully get away with that, so may be best to just eat the one night of points.

Lastly, in terms of that early of the check-in, probably not going to have tons of luck. Usually night auditors do not run the reporting for the current night until about 2-3am (and deliver bills under door around 3-5a). This would mean you wouldn't even be able to check in until they close the prior day out. You may have luck around 5am after all is closed out in the system from the previous day, but your experience may vary and may be worth a call to the hotel

If you really need/want to arrive at 1am, then make a 2 night reservation. And call the hotel the day before to let them know you will be arriving late.