Two weeks ago, I changed my flights from a
CO E-ticket to a NW operated (codeshare) flight. I changed my reservations via the
Continental elite line, and the day of my flight, had to to have CO convert the e-ticket to a paper ticket. I then checked in with NW.

As far as changing to a direct flight to/from a hub, I believe UpgradeMe is correct. When I contaced the elite line, flights I have seen listed in the timetable, as well as on the COOL travel site as codeshares are not listed as codeshares to them (so they say).

I do not know if they will allow you to go standby. If you change your reservations, I am sure the fare will be much higher. If you purchased your ticket through COOL travel, maybe they can make the change for you because they seem to offer the codeshares CO reservations desk can't.