Not sure if I can answer for a 2018. The band on my rear driver's side boot on my 2021 broke off and the dealer fixed it under warranty (of course, it was within a few months of purchase).
In looking at it, I think you can find the bands and tools pretty cheap and do it yourself fairly easily. YouTube is your friend.
The big concern, however, is whether dirt got inside the boot or if axle grease escaped. If you caught it pretty quick and haven't been mudbogging, you can probably do it yourself. Watch the videos where they cover packing grease in the boot.
Best.