I currently have one factory DB9 remote that is fully functional; however, I do not have any documentation concerning the codes associated with this remote.
If I purchase a second Volvo remote, will the dealer be able to pair the new Volvo remote and keep my current DB9 remote functional? Or will the dealer require the codes for the currently working DB9 remote in order for me to have two remotes when the pairing is competed.

 

Yes, if your current key has been already registered its stays functional when a new key is added, unless someone removes it from the car. You can always add a new key (up to 5 remote keys), however you need an unique code for the new key to be programmed. Each key has its own code, otherwise cannot be register in your car.

 

Whats the cheapest/basic OBD tool that can program remotes on these cars?

 

I have a MaxiSys 906, which is a very good diagnostic tool for my Maserati.
The functions on the DB9 are not as extensive as compared to other cars. There's still a lot of functionality; however, it does not program remotes.
I believe only the dealer or Volvo specialist can do this.

 

Dealer sourced AMDS scanner is required, most dealers typically charge 1hr to program a key I believe. Like @chrzesm said, you will need the key code that comes with the new key, otherwise its a paper weight

 

Will an AM dealer be prepared to program a Volvo sourced remote?

 

I do not see why not, most dealers are cool with it help out customers. Remember though, if you supply your own parts and it doesn't work out, you're beat. LMK how it works out, would be nice to know for a future reference!

 

Take a gander at Aston Martin Key Repair (Google them and on Facebook), they can supply new internals (and full keys) with codes cheaper than any AM Dealer (they deal worldwide too)