Is possible to replace objects of the same tipe en mass on a single cell ? ( Not the entire worldspace ) ....

in your object window for the cell, select all the objects of the same type, then "activate" the render window (like press middle mouse click to make that window active)

hit Ctrl + F to replace all selected items with a new one

Also, if you want to replace all instances of a particular item in a given cell, you can simply click on one of them and hit control-F. Then in the box that pops up, deselect the option "Selection only" and select the option "Cell only," and all instances of that item in the loaded cell will be replaced with the item that you choose.

thankyou ...