Oil and servicing.

Hi few questions in relation to my mk 1 octavia vrs. Purchased car from main dealer ex company car with 59k, car seems to be on variable servicing and as such was serviced at 19k 29k 39k 49k, she is now on 61k dealer said that a service would not be due until Nov or if light came on? Cant help notice that the oil is looking a little dirty.

what oil should I use if I want to change it myself, fully synthetic or semi and is this dependant on what it has been given so far? will this affect service lights? Or should I just get it serviced on fixed intervals as my annual mileage is now very low?

Thanks