Are Saudi Sim Cards simply plug n play for UK people?

I've got a Nokia phone on the Virgin network. It also uses the T-Mobile and Orange network at times as they have an agreement amongst themselves.


In Saudi do the popular PAYG sim cards (Mobily? etc,) just pop in and away you go?
Or do I have to make sure my mobile phone is unlocked to all international networks before I travel?
And do I have to make sure my phone is a certain "band" as well? (I think it's a quad band phone).