The 128k KB, is a little smaller than the Plus KB....
Mine wasn't too terribly yellowed...and it cleaned up..ok, for it's age.
I did pull off all the keys, cleaned 'em and the KB..and put 'em back on, and it works just fine...
Tearing down a 128k, and cleaning the heck outta..I'm amazed how simple that mac was...it sure created a stir when it first hit the market place in early 1984...But the lack of an fan,did cause some heat related issues, and board failures..especially the flyback...