You can send a GW now....there is a [small] risk though that the OC notifies the CA and the CA increases collection activity. Just FYI in case it is within SOL.
I always liked sending PFDs first for a number of reasons. First, the CA is hurting you more than the CO from the OC. Second, you can always include within the GW that you had paid the debt with the CA (e.g. you're humbling yourself by owning up to the debt). Finally on a scoring standpoint, some OC COs could actually be helping your FICO. Personally I've lost points due to removing old COs because the length of history helped more than the baddie hurt. They still help your AAoA and length of history if older and going back to #1, you can always eyeball to see if you need additional points or not and to figure out if it would be worth it to pursue a GW deletion by that point.