like kirstey said, do what it takes to get it in on the airfield. If you suddenly have no oil pressure, you are an emergency about to happen. For myself I would land next to the runway or on the taxi way... somewhere... you dont have a choice in the matter because the donkey could quit at any moment.
Every instructor that I have met is VERY aware of where their student is at any time that they are not in the aircraft. If you could hold in the circuit, I would definitely bet that they would be very well aware that you are a first time solo student and would be making every effort to clear the runway for you. If they couldn't, you can bet that they would get a plane up in the air to lead you to a diversion field and this would be decided quickly.
The main thing to remember as a first solo is that you are NEVER alone ! ! ! ! ! !
I can't emphasize this enough. They will follow you around every inch of the circuit on the radio and visually.
If you have a problem then all you have to do is keep flying and they will help you to decide what to do.
If you have an engine failure.. well like jonathang says you should be able to glide to the field and you already know how to land otherwise you would be up there. I realise that a PFL at this stage is a bit of a challenge but all you want is to walk away... If the aerie gets bent and bugg@red, thats ok as long as your are in one piece.
cheers
Sky