First you need to prime the entire wall with an acrylic primer. This will help to stabilize the questionable surfaces. After the primer has (overnight) you can lightly sand the wall surface to remove any balled up paper areas. These will be easy to see after priming.
Now you will have to patch all affected areas with 2 or more coats of drywall mud. Sand the patches smooth and apply another coat of primer to the patches.
After the patching a texture can be applied. Orange peel is is fairly easy to do but does require some practice to get right. I recommend renting a texture machine (hand held hopper and air compressor) and practicing.