The easiest way to capture the sound of a choir is to place several condenser microphones 6 to 10 feet away from the choir. If necessary, you can use inexpensive dynamic microphones, but they will not be as powerful or clean-sounding as condenser microphones. Also, you will need one stand for each microphone. Alternatively, you can dangle the microphones from hooks on the ceiling.
A powered audio mixer collects all the different audio signals, such as all the signals coming from the different microphones and the CD player and combines them into one stereo signal. You can connect speakers directly to a powered audio mixer. If you have a very large church, you may need to buy a professional-level mixer and a separate amplifier to power the speakers.
The CD player you purchase must have the ability to connect to your powered audio mixer. Most "rack-mount" CD players have this capability, but it is possible to find cheaper consumer-level CD players that will serve the same purpose. Look for a quality CD player that has output ports called phono plugs (sometimes called RCA or "red and whites").
Since many powered audio mixers are sold as packages, along with speakers designed specifically for use with them, it may be easiest to go to a music-equipment store and see what deals or promotions are in effect. Otherwise, you will have to do some research to find out which speakers will work best for your church. One way to determine this is to rent a sound system for a day from a music-equipment rental facility and test it out. You will spend some money on the rental fee, but it may help you save money in the long run.
You will need at least one XLR cable for each microphone. You may need more than one for each if you will be chaining them together to cover long distances. You will also need connection cables for the CD player, the audio mixer and the speakers, but all these may come packaged with the equipment when you purchase it. Again, buy only quality cables. Cheap cables will sound bad and break quickly.