Congrats! I have one, this was my thought process.
Switches, lights and flippers are wear items which I wouldn't care too much about them. However, by running Dr Pinball through the service menu you can see if any are out.
More importantly I would be concerned about cabinet and playfield condition, this is what differentiates the HUOs. As previous poster said, check the areas where Cliffs would covers (Shire, Gimli, Orthanc), all of the playfield plastics for cracks (these can be difficult to find), and wear on the playfield (shooter lane is normally a good indicator of this).
If you buy, first additions should be new balls, Pinbits plastic protectors, and Cliffys. The LOTR owner's thread has a lot of notes about small gameplay issues. https://pinside.com/pinball/forum/topic/the-lord-of-the-rings-journey-begins-members-club
Shameless plug, when I bought my LOTR I wrote up a guide on my blog how I moved it to ensure no cabinet damage! http://toddnappi.blogspot.com/2013/08/how-to-properly-transport-pinball.html