You can attach mdf file to SQL Server using the below code:
CREATE DATABASE TestDb ON
( FILENAME = @'C:\MyFolder\TestDb.mdf')
FOR ATTACH
GO
In reference to your question, itz advisable to remove the existing full text catalog and adding a new catalog with the same name. When upgrading a server instance to SQL Server 2008 R2, the user interface allows you to choose three upgrade options: Import, Rebuild and Reset.