If you know you're in the wrong section, why post a topic here??
To help answer you question a bit tho... go to repco and ask for trade price... if you want it cheap... they'll generally give stuff to you cheaper if you ask... or just wait till boxing day cos I think repco and supercheap have 25% off sales or something
Or just go to Nissan and pay thru the nose....
Otherwise, take it to a mechanic and get it done properly...
Being 100000, it will prob be a good idea to do timing belt, water pump etc unless they were recently changed. maybe also spark plugs, oil, fuel & air filters, depending how regularly it was serviced previously.
regarding oils.... depends how much you want to pay too.... you could go fully synthetic and pay $70 a bottle.... but it looks like you're trying to keep it as cheap as possible... in that case, maybe try a semi synthetic like Motul turbolite for about $45.... again, its all about preferences
anyways...... hope that helps a bit.