You do not need to serialize values. If the value needs to be serialized, then it will be serialized before it is inserted into the database. Remember, resources can not be serialized or added as an option.
If the option does not exist, then the option will be added with the option value, but you will not be able to set whether it is autoloaded. If you want to set whether an option is autoloaded, then you need to use the add_option().