O2 sensor question

I replaced the exhaust pipe just below the header, the one that goes from 2 pipes to one just before the cat converter. First, the gaskets where it met the header didn't fit flush, so I'm guessing I may need to double the gasket to get a good seal, it's a Walker exhaust. Second, I wasn't able to remove the old oxygen sensor to use on the new pipe, will it harm the car to drive it for about a week until I can get a new sensor in there? I will be leaving the car with my wife while I travel for a week, so she'll be driving it about 20 miles a day. It seems to run fine without the sensor in there, I've put a temporary plug in the hole where it goes. James F. Hodgdon Jr. Hodgdon Scale Models