The pre op is meeting with a nurse (At my hiospital id never seen her before or since) who will basically check you are fit for surgery. Blood tests, weight, blood pressure etc. Are you meeting your surgeon too? I would ask surgeon about possible side effects. What he/she will do if they find the cancer has spread further than they thought. Do they know what ward you will be on already (so you can tell visitors in advance)
I remember my pre op day. Meeting with surgeon in morning and pre op assesment in the afternoon. The pre op was massively overrunning ansd i was there HOURS. Be prepared for a wait. It does bring it all abit closer so be prepared to be a bit wobbly after (emotionally)
Hope it goes well and on time!