How to remove abscess packing and clean wound?

Simple and easy. You should have received instructions and dressings but some simple rules are expect some pain and bleeding in the early stages of healing when removing packing. Removing the packing helps remove some of the "bad" stuff. Cleanse gently with saline or wound cleanser to minimize damage to healing tissues. Repack loosely to minimize further damage to the wound and keep it covered and protected.
Depends. It will depend on the size and location of your wound. Risk for pain, bleeding and drainage are also factors to consider. Hopefully you have instructions from your provider. If not, then okay to call in, or go in for advise. That provider knows your case. Be well.