You do need a laptop, and the apn program from texe, also a udl lead, the apn can be found online for the provider of the sim if its ee,vodafone,o2, others are there as well, some providers dont need a user name and password but this should be with the sim info if needed.
programming it only takes about 1 min and its saved in the GSMcom so even when powered down keeps the info.
If the customer is to supply the sim you will need to tell him if he has one that has a fixed ip he can remote access it but if he has just got a vodafone,o2,tesco,EE one he can not remote into it.
I hope this helps