how do i change a timing belt on this model

You are going to want to purchase a Haynes manual or similar book which will show you how to do this. Basically, this is a very complex job which requires precise reassembly to avoid major engine damage. You will not need to time the engine afterwards but you will need to make sure the cam and crankshaft pulleys remain in the same alignment as they were before you started. It is far too complex to even give you an overview here, so again, I highly recommend purchasing a manual before you decide if you want to attempt this repair.