Mounting a red dot - front sight

[another okie]

I have an inexpensive red dot I bought to go on a .22.

I thought it might be fun to put it on my AR, (A3 model), but the red dot hits the front sight. Now I realize there are risers and there are also flip up front sights, but which works better?

Which is cheaper? It looks like replacing both sights is expensive.
How do I mount flip up front sights?
Do they just replace the screw-in front site or do you have to replace more parts?

I am only moderately handy with tools.

 

[iamkris]

You can get a cheapie riser mount for a flat top for about $20-30. Do a web search for "riser mount" and you'll get several good hits.

 

[Black Snowman]

A riser is simpler and much cheaper than flip-up sights (AKA BUIS or BackUp Iron Sights).

 

[Carlos Cabeza]

Brigadoon Military Surplus on Sunnylane IIRC has some A3 mounts that are very inexpensive.