Firstly, thanks massively to you guys who awnsered my previous decal related discussion, you were a massive help!
so here is where im at. I managed to get round origional issue and am now able to add custom decals. however, once i had my new decal selected, i then went into the mapping window to select the surface that i wished to place the decal on (i.e. the front screen). initialy i had the problem that, despite selecting to place the decal on a single face it still insisted on covering the entire part. i managed to get round this by first slecting the desired face, the adding a reference and selecting the same face. im sure this isnt the best way?
also (as if im not a pain enough) i have deleted the decal, and though under the decals tab it now says "no decals assigned" the image still displays on the screen! (see attached image) a little confused??? lol
p.s. please excuse my amatuerishness!