I haven't used this pic before but i can't see any major difficulties in setting it up. You already seem to be able to start and service interrups so i won't deal with that. Initialize the timer with ....

TMR1L = $10
TMR1H = $2D 'Start timer with 65536-54000=11536
T1CON = %00110111
' here you should input code to enable the interrupt

..... in your ISR you should reset the timer to $2D10 again, increment your fivedaycounter and reset the interruptflag.

Perhaps it would be easier if you posted your code and i'll make the changes that are needed.

/Ingvar