Oxygen Sensors

I have a 1997 LeSabre and it coded telling me I need to change the O2 sensors . Money is tight and I know they both should be changed . I was wondering if one of them is more likely to go before the other one . I would change that one first , then the other at a later time .
Any input would be greatly appreciated
Thanks
Gerry Lucas

I had no idea there were two O2 sensors...

The Northstars have 4. One in each exhaust manifold, and one in front and in back of the cat.
(At $100 each).

Check with your parts store and see if the same type is used front and back. If they are the same, buy one. Flip a coin and change one, keeping the old one, if the code is gone you got lucky if not take the old one and replace the one you did not change.

You have two??? Where??? Anyway, If money is tight, check a salvage yard. Most guarentee their parts for 7-30 days. Way, Way cheaper than buying new.