When you buy a Plus/4 system from Ebay, expect the "CPU" chip, the 8501R1 (or 7501R1), to be dead. The classic symptom will be a pattern of small orange horizontal dashes on the screen, and a failure to initialize into BASIC. I was fortunate to find a source for these chips, no longer available by the way, and fix the system you see here.
The next obstacle one must overcome to making your Plus/4 system useful is to find software. Most of the Plus/4 software was written for the PAL version, and very little will work on an NTSC system. I have searched extensively and collected the "best of" programs for NTSC and posted them on my web site.
There once was a Plus/4 user group "PLUG" that distributed NTSC diskettes. I have been unable to find anything about this group, other than what I found from the third disk in the series.
The Commodore CM-141 seems to be the right display for the Plus/4, at least color-wise. It also has jacks in the back compatible with the outputs from the Plus/4 video and audio.
Lastly the joysticks ports are not compatible with the C-64 (or most anything else) so you have to find or make a jack that will fit the small round DIN plug.
More photos of this system with screen shots of programs, etc.
If you're looking to buy a 8501R1 (7501R1) CPU chip, let me know I may have one available for sale.