don't need to use new pads if they are in decent shape but you HAVE to bleed them. Air in your brake system can make your pedal go to the floor with no brakes. You don't want that! (Neither does the guy in front of you!)
Also have you installed the brake bolt mod? I'm just wondering if your rear brake calipers never came on before and that is why they needed to be replaced. Probably one of the cheapest and best modifications you can do to your car (Assuming it's a Impala and not caprice but since you have a rear caliper I'm assuming you have an impala or a caprice with rear disc brakes)
1994 SS - GRAIL Webmaster, St. Louis, MO View our Tech/Guide page for everything from your basic oil change to Manual transmission swaps!
Had to buy a new brake caliper for passenger rear, do I have to install new
brake pads as well? Do I have to bleed the brakes too?
New pads would be best, but really depends on how much is left on the old ones. I'd just do it for piece of mind. You should check the condition of your soft brake lines as well. You will need to bleed the brakes. It's been mentioned to you many times already and no matter how many times you ask, the answer won't change.