Hello Jerry
This would probably be better posted in the Software Arranger Forum on the Synth Zone, but hopefully the following will get you started.
OMB will get you started http://www.1manband.nl/omb.htm as this is a software arranger, (A Demo version can be downloaded so that you can try before you buy) it will use the sound card in your computer, so the quality of sound will be determined by this, however when you are familiar with its operation it can be setup to use other software instruments. (VSTs etc)
OMB also has the advantage in that it will play Yamaha styles, so you will have plenty to be going on with.
I have deliberately not mentioned any style converters or software instruments, as to try and do everything from the off can be very confusing, so post again when you are familiar with the use of OMB.
If you have the money, have a look at Wersi’s OAS range of instruments http://www.wersimusic.com/organsx.htm and http://www.wersi.net/ (You can use Babel Fish to translate http://babelfish.altavista.digital.com/translate.dyn )as these incorporate everything in one box, and operate exactly like any other arranger keyboard, but have the advantage of being able to use Akai samples and VSTs, and like all computers and software, are easily upgraded.
Hope this helps and post again if you need any further help.

Bill