This question is probably better asked in a place like the
www.kvraudio.com forums.
In brief, to save workstation "projects," you have to do a MIDI SysEx dump, and use a MIDI SysEx librarian program to record it. To re-use it, you have to load the dump, and play it back to the synth, to re-load the composition into the synth.
To save the audio to the computer, you generally have to plug "sound out" into the "sound in" on the computer, and use regular recording.
An alternative is to make the MW-7 play the entire composition out through MIDI out, and record it as multi-channel MIDI in in a sequencer on the PC. Then, to play it back, you have to set up the right voices/instruments/patches on the synth, and start playback in the sequencer. You probably want to use MIDI Time Code and/or clock to do the recording, so that you get beats/bars right in the sequencer. Although if you don't, it will still work, as long as you don't quantize or otherwise edit the data after it's been recorded in the sequencer.
Although, in my honest opinion, what you really need is a good software-based workstation. Something like Cubase Studio or Cakewalk, with a bunch of "soft" instruments, and do all the recording and production in software on the PC. A good soft sampler like HALion or Kontakt will go a long way towards filling the need of voicing different instruments.
Keep the keyboard as input keyboard for recording phrases, but don't use its sequencer or voices anymore.
