A glass screen protector can usually be easily removed by placing a fingernail under a corner of the screen - and lifting slowly/gently. As you lift the corner, the adhesive will relax.
If the screen protector is itself cracked or broken, you will need to be careful of any broken pieces or shards - although the laminated construction will usually keep the entire screen protector together.
If the screen protector alone is damaged, it has served its purpose in protecting the expensive iPad screen. After removal, it is easily and cheaply replaced with new.
If the iPad screen is seen to have suffered damage after removal of the screen protector, you’ll need to consider either repair of the iPad (entailing a screen replacement), or replacement of the iPad (for older models of iPad, this may be more cost effective.
iPad Repair & Service - Apple Support