Are you worried about being able to print on their pre-cut card stock? If you're worried, perhaps do a couple of test prints on card stock that you cut yourself before you place an order.
I made invitations for a family reunion last summer using the pre-made pockets from Cards and Pockets, and they turned out great. Rather than try to print on pre-cut card stock, I printed everything on 8.5x11 card stock and then trimmed all of
the inserts to size.
If you're still worried, perhaps ask friends and family if anyone has any design experience or knowledge using Adobe Illustrator or Photoshop. I know some ladies have been able to create their invitations using PowerPoint. Or consider hiring
someone to do the graphic design for you and then you do your own printing?
Cards and Pockets offers printing services too and pretty affordible prices.