Alright I have a few questions, after reading Fine Scale Modeler (great magizine).
My first question is this... What is the base color or primmer color on the M113's??
My Second question is... What is the standard paint job for this kind of tank
My Thrid question is.... Has anyone built this model before. Its made by Academy

if you meen the m113 fitter by academy, well i made it.
1 tip: don't forget to put the hydraulic air cables on it... so many times I see this model with a great paint job but a lack of this very noticeable detail.
as far as the painting academy gives a good guide but since the IDF uses a more olive color these day's you will have to do some mixing and research.
here is an article on the paint:
this one : http://idfmodelling.free.fr/article01.html
note that the modern color has been changed and is not the 1982 color
this one: http://www.webone.com.au/~myszka/IDF/Research/paint/sandchip.htm

for my model I used a mix of tamiya desert yellow and olive green 50/50 and if i remember some buff or medium gray just mix it next to a pic to get the right color.
anyway don't mind if you get a diffrent tone of color I heard that the tone diffrence from the north of the country to the south.
for the base cote I don't know. I didn't use one
hope this helps