tumbared, It is important that you understand exactly what equipment you have and what software you will be using. Otherwise you might get stuck in a situation where you won't be able to "musclepower" through it.
It sounds like your PLC is of the MicroLogix platform and you will thus be using RSLogix 500. This is unfortunate for many different reasons. The Compact/Control Logix are better suited for this application. They have pre-defined Add On Instructions, pre-defined tag structures, and can be easily put on the EthernetIP cyclic communication. There are also numerous code samples for the Kinetix 300 for the RSLogix 5000 platform.
That being said, you can still control the drives with a ML1100 or ML1400. The drives close their own position loop and serve as stand alone indexers so the integrated motion control stated by others is not a requirement.
Unfortunately, you will have to develop all of your own messaging routines in RSLogix500. You will have learn a lot more about the drives and will have to understand how to format the messaging to access the drives parameters correctly.
Start with this manual here.
http://www.cednebtrc.com/ftp_bbernier/Kinetix 300 User Manual.pdf
Appendix G deals specifically with RSLogix500 messaging to the K300. They don't give you much, but it is enough to get you started.
The drives themselves are setup simply by using a web browser. They default to an IP of 192.168.124.120. It is good practice to hook directly up to each one and configure the IP properly before plugging them into your network. The fourth octet can be changed using the front keypad. For reasons nobody has ever been able to explain, octets 1,2,and 3 need to be changed while online. It is probably just a holdover from the orginal Lenze firmware of the 940 drives.
Go to Rockwell's website and search for some sample code. You will find most of what you are looking for has already been done. It is just a matter of massaging it to fit you application.
Although not common, it is also possible to control these drive with a Logix500 series controller using simple step and direction signals. In this manner you would treat them as stepper drives and the Ethernet connection would be optional for control purposes.
Good luck, you have a lot of work ahead of you!