Deploying MCX with InstaDMG

Hello, please forgive me if this has been answered elsewhere... I'm a bit new and haven't been able to figure out the answer to this yet. I have MCX files created and am dropping them into my InstaDMG images with a package. This part works perfectly; but I still need to edit the entries when the machine boots. I took a script I found in these forums that works perfectly, however I'm not sure how to get it to run on first boot only one time. I tried using launchd by placing the script and the plist in the correct spots with a package. However this did not seem to work. Is there a better or easier way of doing this? Oh yeah, I also have another script I need to run once upon first boot to set ARD, VNC, and SSH settings. Thank you, Ken