I found a work around for the problem, for those of us who are not programmers and are taking a while to learn how to replace the kexts needed to fix the problem.
I found a video showing how a guy tried the Virtual 5.1-surround USB 2.0 External Sound Card, a usb device, to get rid of the hiss.( less than 2 dollars on Amazon, ships from China)
I had a Syba SD-CM-UAUD Sound card laying around, and it worked! (7 dollars from Newegg and ships in days, not weeks)
It gives me time to learn how to replace the files needed to get the problem fixed, at my leisure, and without the frustration of that constant hiss.