Originally Posted by dizzlmcwizzl
Interestingly I think woodrow posted something not long ago that an officiated match you would not be allowed to to change rackets.
Do you mean 'can't without getting a delay warning/penalty'? Because anyone can take more time than is allowed - as long as they are willing to suffer the consequences. On the ATP tour the chair would certainly allow it - and give the server a first serve.
As others answered - it's easy. In a regular non-officiated match you can switch but have to give the serve a first serve.