Here is a link to the thread I started last year about this subject.
http://www.cadillacforums.com/forums/cadillac-srx-second-generation-forum-2010/271353-2010-2012-grille-upgrade-2013-a.html
I was one of the first forum members to do this grille swap. Yes, I did it without removing the whole front end.
Here is a quick write-up on how I was told to perform the swap:
"...Hello. the instructions that come with grille are basicly are to remove the facia, then you transfer the grille over. But you can remove the grille without taking the facia off completly. but it would be hard to explain. first you have to pull the top trim off above the grille. then drill out the two rivits. remove the 10mm hex head fasteners on the top that hold the grille to the upper bar. then you have to pull on the ends at the top and remove the two push pins at the side top of each end. (These are the same type of push pins you needed to remove to remove the upper plastic cover earlier.) they have to come out before you try to remove the grille. then each side has 2 retainers that push through the facia but they are tricky. you have to move them back and forth while pushing on the grille so that the grille goes in towards the back of the vehicle. ( I used a sharp thin tool to help release these "Wedge" type fasteners. Once you see these clips, you will know what I'm talking about.) they are kind of like wedges that have to fit through a slot. so a little pressure and wiggle the tabs back and forth a little untill you get it through the slot. the bottom has about 6 of them but some of them come out with out any help but usually the two center ones will need to be moved up and down while pushin in on the grille. (I used a putty knife to release these two lower center tabs from the front. Between the chrome grille and fascia being careful of the paint on the fascia.) they are slotted horizontialy. and you have to do them by feel cause you cant see them. the new grille goes in very easy. just line up the 2 on each end tabs then the bottom ones will line up. push the grille forward while holding the facia. carful you dont want to break any of the tabs. get your hand inside behind the grille and push right at the fasteners so they snap all the way in. then put the hex bolts in and tighten them. now push on the facia at the bottom to seat the bottom fasteners. then install the two rivits. and the top peice. if you have headlamp washers then you will need to remove the hose assembly from the bottom edge of the grille after the fasteners are all removed so you can get to them. Good luck hope all goes well. take a look at the new grille to see the wedge shaped fasteners. dont push on the chrome , push on the grill frame. so as not to break the tabs..."
Keep us posted on how your swap goes. If someone needs advice, Just shoot me a message. I'll try to help.
Thanks Ken