Depends on how you look at it.
Nothing major from the 81 to 82 years of single-overhead cam bikes. Biggest being the front brake switched from disk to drum for the '82 model year.
Pretty easy to spot the 82s. Fenders were painted black, forks painted black, engine painted black, headlight bucket black, headlight mounts black, carbs painted black.
Everything works the same though. Almost every part is compatible between the 80-82 model years.
Just be careful of anything listed for '82 bikes only as it may be for the double-overhead cam XS400 that was introduced that year, and is 99.9% incompatible with your bike.
In that sense from the 81 SOHC to 82 DOHC XS400, everything changed.