Originally Posted by mbreuer
2. Yes, but you have to go through Delta. I'd do the same as above - don't purchase until you've worked out the details with Delta. It is possible that you would have to book the CO flight as a Delta codeshare - but I don't think so. Also, the rules (fare class, etc.) might be different - check with Delta.
Entirely incorrect. You cannot upgrade a CO flight with DL miles. Period.