What exactly is your problem?
There are ftp clients for MacOS, like Interarchy, Fetch, NetFinder, ..., so uploading shouldn't be the problem. If you don't have shell access to your webspace, you can unpack the Geeklog tarball locally (using StuffIt Expander as usual) and upload the files using any MacOS ftp client. To edit config.php and lib-common.php, you can use a text editor like BBEdit or Alpha (don't use SimpleText).
bye, Dirk (on MacOS X)