gruezi tokiovd (gruezi = Hi in swiss-german)

for the fastest (and most competent) answer to your general question I recomment that you post your question under the Delta forum on this Flyertalkboard.

and as a title there, I recommens that you psot something like 'how can I upgrade a/my Delat flight'.

Good luck (I am not a Delta Frequent Flier, though not very competent to answer your question).