Guys, I should have updated this. I found the solution to my problem with the error messages it was generating. Turns out, when the "GM Instruments" zip file was uncompressed, it forgot to uncompress most of the GM Instruments in the Samples folder. I tried uncompressing the file again, and this time it was successful in uncompressing all the instruments. So, problem solved.

The links that DSK sent me for sfz format are sfz files only. Neither GM Instruments nor Orchestra 2 files are SF2. They're all sfz.

At DSK's website, I watched a demo of the SF2 soft synth and was fairly impressed with its capabilities. And, since it was free, I d/l'd it. Then I sent an email to DSK, requesting the archives in SF2 format, and he sent me a set of links for the SF2 files. I've uncomrpessed about half of them so far and haven't set up SF2 yet, but I will. If it's easier to use than Sforzando, then I'll probably start using it instead.