box uvw to each in selection

Ive read most of the

Ive read most of the "MAXScript Essentials" book, which is pretty nice. But imho you will learn a lot faster in conjunction with video tutorials like the "MAXScript 101" on the start page:
http://www.scriptspot.com/

About arrays, Anubis has published an article of using them in MAXScript:
http://www.scriptspot.com/3ds-max/tutorials/lets-play-with-array

Cheers

You should avoid using the

You should avoid using the "$" character when working on a selection of multiple objects, as it can reference subanimations instead of nodes. Better loop over your selection and use the loop index to reference the objects in the selection like so:

for i=1 to selection.count do
(
    selection[i].wirecolor = random black white
)--end for

About your problem:
If you see something like this in the help file:
< void >< EditablePoly >.SetSelection < enum >selectionLevel < bitArray >selection

It means that the command "SetSelection" will return nothing (void), will work on EditablePolygons only and you have to give it the selection level as a enum value (#Whatever) as well as a number of polygons/vertices or whatever to work on as a bitarray value (#{1,2,3,5..12}).
Example:

myEPoly = selection[1]
myEPoly.SetSelection #Face #{1..10} --will select the first ten polygons of that editable poly
myEPoly.detachToElement #Face keepOriginal:off --will detach the selected faces as an element

I guess what you want to do is to select some polygons and detach them without the dialog popping up? Then there would be no need to set a face selection, just use the detach command.