You won't have to remove the firewall but you will have to drill out the rivets around the perimeter where you will be putting camlocs. The engine mount will continue to be well-supported by the firewall/mount attachment to the structure behind the firewall.
I'm not sure you'll be so lucky with the cowling itself. Since the hinge strips are (or should be) bonded as well as riveted, you may have some difficulty removing the strips. After that, it should be easy. I relied on the lip that Van's molded into the cowling for fit and extra structure for the receptacles between the firewall and spinner but it's not really necessary if you use broader attachment strips, similar to those at the firewall. Don't worry about minor damage to your cowling as you will want to fill all the existing holes and bond the new receptacle strips on. I'd also recommend a single ply behind the cowl along where the grommets will go, to add strength where existing rivet holes might overlap or be near a grommet.
Once the cowl is refitted, you can fill any small damage. I don't think you will need to adjust the fit but you can if you had some issues with the original fit. If you do and your adjustments leave some gaps, this is the time to fill them. Then repaint and you're done.
