Hi there
Yes, you need to use the SetTimer command, with an appropriate preload value, and the SetFlags command to set the interrupt. Look at SetTimer and SetFlags in the manual because it describes the detail. If you are using an external crystal then this will be very accurate.
Basically the internal timer has minor ticks and major ticks and the preload value sets the tick rate of the major ticks and how the Timer variable is incremented. When the timer variable overflows it can cause an interrupt (if you've setflags appropriately) and you can then update you 7seg displays in your interrupt routine.
Hope this gives you the general idea.