You may not have to buy anything. A month is a LONG time to let a car sit, especially a modern car that has things consuming small amounts of power during that time.

Jump start it, if it starts, see how she does in the next couple of weeks after you let the battery charge up. If you can start it without problems at least once a day for the next 1-2 weeks afterwards, I don't think you need to replace anything.

BTW - If your Monte has a battery that requires water, might be worth giving it a little check before jumpin' it.

 

my battery will go dead over storage.....even though it's a fairly new battery and still under warranty.....i prefer to leave the cables on even though it was always said to disconnect them in storage for the winter .....but with the electronics maybe the should always have power to them.....i usually run it on a trickle charge for 24hrs. before i start using the car....gettin' real anxious to take it out but snow forecast this weekend...bummer....

 

If you are not intending to start the car weekly, disconnect the battery. The electronics in the car could care less if the battery is on or off, but if you are not starting it weekly, it will drain the battery. ANd a trickle charger seems a bit silly to me unless you are doing that to charge the battery when you are preparing to take the Monte out.

I winterize my Monte, disconnect the batter and don't worry about it until I get it out for spring/summer driving. I don't think I've had any issues starting it right away when I reconnect the battery (as it still held a charge of winter).