Guitar is my main instrument and I usually end up in rock and metal projects. But I have a cheap keyboard that I write all kinds of genres on - classical, jazz, blues, etc - just everything.
I have SPLAT, which includes Rapture Session, Rapture 1.22, and Dimension Pro 1.5
On my cheap keyboard ($300 Yamaha), I would handwrite the scores in music then step write all the notes in the keyboard's memory.
So I purchased the Alesis V49 MIDI controller.
Is it possible to do that with Dimension Pro 1.5 and Rapture 1.22? Using the step sequencer? PRV?
I have a score that was written for cello, contrabass, violins, and piano - very dark sounding.
I have a score that was written for drums, guitar, sax, bass, trumpet and trombone.
Can you point me to some tutorials that will show me how to use SPLAT, Rapture, and Dimension Pro to step write the notes using my new Alesis MIDI controller?
Or does Dimension Pro and Rapture NOT have the "full" orchestra that I would need?

Thanks!

Start with Tutorial #4 to get the basics of working with MIDI in SONAR
There are a variety of ways to enter MIDI data. Step recording probably is the closest to your old method.

I find it easier to just play(record) the track capturing the midi and then quantize as needed to clean it up. I find this is usually faster and easier for me than using the step recording. With highly syncopated parts, like drums, step recording is best. You can then replace the synth or preset with whatever should be played. Or, if all else fails, you can copy the new midi track to a synth of your choice.
 
To each their own and YMMV.

Thank you for the direction!

I don't know about the second one but I would suggest using SI-Strings and TruePianos for the first piece rather than DimPro and Rapture.

Dimension Pro and Rapture can do a lot.  Your V49 should be fine.  You can use piano roll view and / or step sequencer.  Don't be afraid to make many different midi input files pointed to the same instrument.  In one track you might have a step sequencer section for something repetitive.  In another track, you might have a non-repetitive section that you stepped out but with both pointed to the same vsti.  I've been known to use step sequencer, bounce to clip, move the clip and aim it at the same instrument and start again with a different step sequencer sequence....
 
The cakewalk shop has video tutorials that have midi sections.  Groove3.com has videos specific to different versions of sonar and they include midi tutorials.  Look for the ones from ELI KRANTZBURG... forgive my spelling.  He explains midi very well.