Oracle MySQL and Percona Server are binary compatible, meaning Percona Server is a direct drop-in replacement for Oracle MySQL (Community or Enterprise). Percona Server does have a few features that once enabled make it hard/impossible to go back to Oracle MySQL, but those must be explicitly enabled and are not often used. In the case of going from Oracle’s Enterprise MySQL Server 5.1.x to Percona Server 5.1.x, you should have no issues, but it is still always a good idea to test it first on a development/test instance to make sure there are no surprises. You basically stop MySQL, remove the Oracle MySQL binaries, install the Percona Server binaries, start MySQL, and then run mysql_upgrade (though in your case mysql_upgrade likely won’t do anything, but it’s a good practice to run it regardless). And again, I recommend testing this on a development environment first to be safe.