In Macbook Air 2018, the storage is flash and on-board. Hence unfortunately the SSD cannot be upgraded.
The only solution to fix broken or cracked LCD of MacBook Air 2018 is to replace the entire Display (Top) panel.
MacBook Air 2018 Display Replacement will come with 1 Year Warranty.
Genuine OEM parts with One Year Warranty will be used for your MacBook Air 2018 Battery Replacement.