Korean Tourist Visa
At this time there is no need for extra steps for a tourist visa.
There is a KETA that has been suspended for US and UK citizens but if you would like to apply you can. This doesn't speed up the immigration process at the airport it just means you won't have to fill out a paper arrival card.
This is where the wedding will be held!
As far as I am aware there is no hotel block service in Korea. But there are plenty of other hotels in Daegu if you want to shop around,