all fields must be displayed?

Hi
I have a question for you,
I use now i similar component dar takes a JSON and renderes a table ...
I wish to use these AW instead .. but i have some doubts :
1) i only need to display some fields of the model ... this is simple i guess ... i can construct a model for the grid filtering the columns of my json .... but my problem would be ... how can i pass a reference of my json to the Grid so i could change also the original model ... let me explain better :
i have a http request via ajax
callback
var json = eval('('+responsetext+')')
now json is an array with , let's say 7 columns , but i only need to display 4 of them

so i can construct a Header array and a COmnuns array with 4 elements to "feed" the grid

but further i made changhes in the grid ... so the changes should reflect in the original JSON ...
I would appreciate a lot a little suggestion
2) can be implemented a CHECK ALL type of check in the grid (in the header part obviously)? ...so when you have a lot of lines you donìt have to check all of them

3) i.ve seen the type of checkboxes appended in front ... but i also need to edit a line ..is possible?