easiest Ethernet solution without opening it up is going to be a SCSI Ethernet adapter. else, I wish you luck on finding an internal ethernet card for your SE and congratulate you on its liberation.

easiest way to get files from it after that would be to use a web browser catered for those with file download capability (there were a few), and then put the files on a webserver someplace locally-- point the SE to the local address for the folder and you're done. saves time and address typing.