BY removing the head you will by necessity have to take the belt off. I suggest that you take particular care to place the crank on TDC and have all the timing marks lined up before you pull off the head. That way if you do not turn the crank and before replacing the head have the cam marks back in the same place then there will be little problem in keeping the timing right. Check your manual and it may have an hydraulic tensioner in which case you will have to physically release the tensioner to fit the belt back on. If the engine has done time then consider replacing the belt as it may be close to needing replacement anyway sand you will be in the process for the head