How to perform two tasks in one loop in Arduino?
Consider using a finite state machine to track multiple tasks.  Specifically, the state in which you send your message once every 5 hours.  And, the state you update your LCD, perhaps once every second.

As your tasks are associated with time, consider using the built in Arduino call to millis() to find how many milliseconds the Arduino program has been running.  This will not block your program.  Instead it will immediately return with a number you then need to manage.  

To create a delay, use the above number from millis() and add the number of milliseconds for the desired delay.  Call millis() repeatedly until it returns the calculated number or a number greater than the calculated number.  Use this to drive your state machine.  Perhaps you only use millis() to count seconds and use software to count up to 5 hours (5 x 60 x 60 seconds).

Note, millis() will eventually roll over as it is of type "unsigned long".  That is, it will roll over once about every 50 days.  If you want to keep accurate timing when this happens, you will have to account for the roll over in your program.