Any AR-15 accessories will fit the 597 VTR. For the handguard, you can use any free float handguard... if it doesn't come with a barrel nut you'll need to get a standard AR-15 barrel nut, but those are easy enough to come by. Any pistol grip is a straight swap, and the stocks can be swapped out as you desire- the OEM collapsible stock comes on a commercial spec receiver extension, but that can be swapped out for a milspec one or even a regular A2 rifle extension if you so desire.
Here's a thread I started on this subject, complete with pics:
http://thefiringline.com/forums/showthread.php?t=397576