I need to replace the front sight of my Marlin 336c with a higher sight (since I have put a Williams receiver sight on). I have a couple of questions.

Is there a standard size for front sights inserts (size of fitting). Or how do I measure what size I need.
How high should I go?
I'm assuming that I can somehow remove the front insert?
Thinking of a Firesight, (if one is made). Any opinions?
Where can I buy front sights?

Thank you.

as far as i remmber when i had to do the same thing.. marlin 336SS. i had to measure from the dovetail up. how far off is your shots from where you are aiming? are they high or low?
i bought a front post from ashely outdoors with the flat top .090 width.

# 962-161-401 from brownells i think mine was a .406" ht.