rain sensor was my situation also..
a few clipes located on windshield must do the job ( by holding your new sensor ,no gluing!)
But if there is no plastic holders ..someone broke them..before you discoverd mulfunction ets...- you need to do some work ..such
new sensor- ( to buy is easyest-cheapest part)
may be ,but sound like you need a new windshield too- 650.00 usd+ instalation...
3) you do need a reset made by mechanic at dealerchip ..in case you want al of this components work together..practically free if car still on warranty ets
regards