Just change the collation of the database using Alter Database statement.

This should change the collation of all Tables and columns to the new collation unless

there is an explicity specification of collation on Tables or columns. If any of the columns in a table has a different collation the ALTER Database for changing the collation will not change the collation of all other columns in the table (it will be the same as before).

Also keep in mind that when you do a export and import from on database to a different database with differnet collation, ALL THE TABLES AND COLUMNS WHICH GETS CREATED IN THE DESTINATION DATABASE (WITH DIFFERENT COLLATION) WILL FOLLOW THE COLLATION OF THE DESTINATION DATABASE. NOT THE ONE IN THE SOURCE DATABASE EVEN FOR COLUMNS WITH EXPLICIT COLLATION

One more thing which is important: even if you could get through all the above hurdles, the change in collation may lead to a different interpretation of the the data for data types like char, varchar and text.