Hi Chris,
Don't know if this is any help at all, but for a Lucee 5 extension you simply copy it to the "deploy" folder in the Lucee 5 install directory (for me it is /usr/share/tomcat8/lucee/lucee-server/deploy/) and then start Lucee and it gets deployed automatically. I'm not 100% sure but it might also do this while Lucee 5 is running as well.
With regards to building an extension the best I can do is point you in the direction of the Lucee 5 extensions that Micha has already built, which are all on the Lucee Github account, for example:
and so on. Maybe you can figure out from the structure and source of these what you would need to change to get the cfspreadsheet-lucee extension working as a Lucee 5 extension.