As long as the calipers aren't seized and are not leaking, you don't need new ones. Even if they are leaking you can replace the piston seals. A little brake noise when applied is not that serious as long as the pads are free and the disk is not heating.
Squealing can be caused by glazed pads. You can wipe the pads with sandpaper to knock off the glaze and clean the disk with disk cleaner. A TINY amount of silicon grease on the steel back of the pads can eliminate the squeal. Don't get any grease or lubricant on the disk.
2004 Rebel 250, 2003 BMW K1200GT (roadburner), 2004 BMW R1200GS(all purpose),
1973 Norton Interstate (in a box in the basement)
1968 Triumph Bonneville