You can obtain an estimated repair cost for your iPad here:
iPad Repair & Service - Apple Support
Apple generally offer two fixed-cost tiers - (1) battery replacement and (2) other damage. If you have benefit of an active AppleCare+ plan, being an insurance product, the cost is reduced to a small excess/deductible fee.
For qualifying devices, in lieu of repairing and returning your own iPad, Apple usually exchange the iPad for a renewed/reconditioned device of the same model and specification. This results in a much faster turn-around for you, at no additional cost.