The easiest way would be to use Library Server + Authentication, enable "Automatically sync changes" and use the standard display on your second computer to edit and manage the library.
Even easier is to use another PC that has it's own unique copy of the library pointing to the same media location as the HTPC.
Over here - my workstation is the "edit" station and has it's own unique copy of an MC library. On this station is where I add all our media, edit tags, drop stuff, move stuff etc etc. But since the actual media I am adding and editing and changing is in the same spot as where the HTPC gets it's stuff from - it's as easy as making changes here (on my edit workstation) and have the HTPC set to automatically scan for changes.
We leave our HTPC in Theatre Mode forever - but when we fire it up for movies (Projector) or music (JRemote) or as a remote client (movies/music on the desktop PCs etc)...all the latest and greatest changes are there waiting ready to enjoy.
Now - I do have a weekly maintenance routine where I pop onto the HTPC via RDP and check it out - but I do zero library maintenance during these maintenance windows. The HTPC master library - that serves our clients - essentially updates itself non-stop as it scans and records media changes - as delivered from my standalone edit workstation.
Also - the MC library on my edit station is much more technical in nature (special views, utility smartlists etc) so serving this kind of library to the family makes no sense as they would not understand it all all. So I simply use the tech workstation library to do all media maintenance and feed the more "basic" library that is our master on the HTPC.
VP