jester, the 3576 and 2160 don't have a program guide for point-and-click program scheduling.
However, if their old LG didn't have a HDD, they'll be much better served with a 3576 or 2160, as you know... no media logistics to worry about.
So, scheduling their programs is prob. their biggest challenge. If they're ever had a VCR, the scheduling is similar except easier cuz the timer programming menu is quite simple... arrow right to each slot for entering time, date, etc. then arrowing up/dn to change the data.
If you haven't already read the help file on Timer Recording, see "Auto-Recording with a Timer Program" here, which shows the menu and explains what goes where.
Selecting recorded titles is also quite easy, requiring only pressing the Title button and pressing Play on a title. The one thing they'll have trouble with there is that recorded programs have no name, only a day, date, etc. plus a full-motion index pic to indicate what that title is.
Since these units have two drives, HDD and DVD, they'll need to be aware of that and shown which buttons (top row, 2nd and 3rd buttons) are used to select a drive... just so they don't panic when something doesn't seem to work or they don't see the HDD recording light someday and think it's not recording.
I think these might be the biggies for them?