Those instructions are for Elgg 0.9. Elgg was rewritten with version 1.0. There is a metaweblog plugin here: http://code.elgg.org/plugins/branches/1.7/metaweblog/

Thank you for your help Cash.

I downloaded, installed, and enabled metaweblog and went through the steps in the previous link again while pointing to the metaweblog.php file and changing the blog type to "Metaweblog API".

Unfortunately, I still get an "Invalid Server Response" error. Any idea what the reason could be or how to get this working?

Thank you again Cash.

Never used it. Sorry that I cannot provide more help.