If you have access to phpmyadmin the best way in my opinion is to get WP migrate Db Plugin, then create an export sql file with new url address and upload it with PhpmyAdmin.
That way you ensure that every place in the site with old url get replaced with new url in a safe way (you can’t do a simple search and replace because it won’t work)
Regarding your 2 questions:
1 With this plugin is pretty straight forward. Create a database backup just in case, but you shouldn’t have problems
2 No problem if is replaced this way.