A welder won't stop the car from being driveable at all, its just when parking etc you get some funny looks as it skips about, normal size roundabouts etc you don't notice it. If you've got the money you could just get an LSD though if you'd rather keep it nice to drive normally at weekends, but yeah definately sort something before you go drifting or the car will be holding you back as it makes it really unpredictable (could grip and straighten up even if your foot to the floor)
