First off, make absolutely sure that the CO fare you were quoted is upgradeable-- the fare code must begin with a K or an H-- that fare sounds about right.
Second, are they willing to issue the upgrades on the spot? Or, would they be wait-listing you-- wait-listing isn't fatal, but it will require a little more research on the current state of the BF cabin-- I'd be happy to help you research same as I'm pretty familiar with that route in BF. No sense in paying double the fare on CO if the upgrades aren't close to 100% certainty.
Now, here comes the possibly money-saving work-around. As jamiel alluded to, you can use OP miles to fly on a NW ticket, booked through Continental. Not fly NW planes with CO flight numbers (which you can do to, but at the same fare,) but rather NW metal, NW flight numbers OR CO metal, NW flight numbers. BTW, you can still earn OP status miles regardless of how you book it.
So, right before you commit, check the price/availability of NW WBC upgrade seats and see if there is any savings-- you may find that the lowest available, NW upgradeable fare is lower than the CO fare offered.
The most desirable flights you are looking for would be NW6009 EWR-NRT, NW6008 NRT-EWR. CO metal, NW flight numbers, BF on 777. Second choice would be the JFK-NRT NW flights on NW metal.
All this having been said, I don't imagine that in this particular case the NW M fare will be substantially less $$ than the CO reservation that you have-- and availability seems to be a major issue on the dates you are travelling, SO, it might be best not to do to much research thereby insuring that you get the upgrade on CO, if it's currently available.
[This message has been edited by JonNYC (edited 11-11-2001).]