I contacted MP Dining via e-mail, and asked them to convert my old MP# to new MP#. I got the reply below.
Honestly, calm down people, lets not see another company with 2 hours hold time. -- Things should update automatically in the coming weeks.
If nothing else, your dines will reflect on the MileagePlus Dining site, and should any issue arrise, there will be a record, where you can track your earning. The dining site is run by an outside company, who would ultimately be responsible for any mileage fulfillment.
Their reply appears below. I have left their phone number for any future reference. But please, there is no need to call!
Dear KWILDNJ,.........
Thank you for contacting us!
As of March 3, 2012 Continental’s Onepass and United’s Mileage Plus program officially merged. Your frequent flyer number will automatically change within the next few weeks on your dining account. There is no need for you to make any changes to your account. To earn dining rewards please continue to dine as usual.
Your Mileage Plus Dining member status and account preferences will remain the same. ..
If you would like to review your account, please contact Member Services at 1 800 555 5116 from 9am -10pm ET, Monday – Friday.
We look forward to rewarding you soon!