I might be wrong but I think your Whistler 1040 may be incapable of decoding phase II P25 which may present a problem for you. If it did however, programming it could be as simple as identifying the nearest P25 antenna site, then referencing the list contained here on RR for that sites control channel frequency (the one in red) and programming it in. Otherwise you might have to bust open the piggy bank for a new radio. Or if you are a real glutton for punishment and tight on money like me you could buy an RTL-SDR dongle for $25 and fish out that old laptop in the closet.