Greetings, eh?!
Seems as though you are soon to suffer the reverse problem we had in Canada...namely going from having guide, to having none.
At least two fairly sophisticated service emulators (supporting S1 and S2 units) were developed over the years, and there are still a few old-timers around who might be able to help bootstrap you. If I recall, you didn't even had to hack an S1 to get it up and running and a serial cable worked just as well as a NIC. Some of you may remember me from the Terbonet days (my 29quid NIC cards were quite popular on the foggy isle) and I still maintain a web archive of the old TivoCanada.com forum and tools.
If you have a reliable source for the guide material (usually whatever you use for MythTV will do and preferably in XML format), then most of the heavy lifting has already been done.
Best regards,
D.