You may find yourself using more fuel, and in the long term it's not good for the engine. As far as I'm aware, bank 1 sensor 1 can be done from the top so a fairly easy job that only needs a sensor socket, about £10 from eBay. I'm sure it's the same as the GS300 which I did last year from the top, in other words no need to crawl under the car or raise it up.