is there anything special I need to know for a M16A1 or is it just like an AR15?

what do you not understand? An m16ai is fully auto while an ar15 is semi-auto. Are you unsure of what parts are in each?

I understand that just fine.    Do I have to take the auto parts out to do it?    Or is just the simple take the grip off,  spring, detent  take selector out and put new in or is there more to it with auto parts.

Loosen the pistol grip screw and drop the grip down to clear the selector detent. Wiggle the old selector out of place, put in new selector.

That's all I needed man.  Just wanted to make sure thanks

Actually if you rotate the selector between safe and semi you can gently tap out the selector just have a similar size punch on the right side to keep the detent from popping up, them slide out selector and slide one in slowly.   I would recommend trying out on a cheap semi lower it's fast and easy.

I have to switch grips anyway but that's a good idea for in the future thank you

The way I was taught (by a former Army armorer, now part-time gunsmith, who has worked on literally thousands of M16s) to install the selector when the detent is still in place and grip on was to use a 1/8" brass punch from the right side to hold the detent down with one hand while sliding the selector angled between 'safe' and 'fire' in from the left side with the other hand.  He said some guys would just wiggle the selector in, but he found using the brass punch was just as fast for him, and did not risk scratching anything when he works on AR-15s for his customers.

Best of luck with your ambi-selector.

+1 for above post. Gunsmith here.

You also need to watch that the selector clears the tail on the sear, as that indexes off the selector.