OK - time to put the record straight...
There are indeed American versions of the QL which were designed for NTSC output (some have a switch next to the UHF to toggle between PAL and NTSC) and a lot more shielding. They were made by Samsung and are much more reliable than earlier models. The QL has RGB-TTL output as with the Spectrum 128
I have sent you a PM with a link to a guy on the TS2068 mailing list who has some QLs to give away for price of postage (they may have unreliable microdrive units, so you may need to get a hold of several and swap the microdrive units).
Apart from the early production models, the QL has proved to be very reliable - the microdrive units sometimes need some maintenance, but most of the time, it is just the small rubber roller inside them which is (a) worn and needs replacing, (b) has ridden up the metal shaft and needs moving back down, or © is worn on the top half and needs turning upside down.
As with any of the 1980s computers, the keyboard membranes need replacing about once every 10-15 years.
I have a stack of second hand UK QLs, power supplies (220V) and keyboard membranes here. Power supplies rarely go wrong - some people had problems with QLs overheating in the past, but that was mainly due to the extra current needed by some early disk and memory card expansions.
As for software - there were quite a lot of games produced for the QL - have a look on the QL Wiki
for details of some (this is very much a work in progress). There are also quite a few Sinclair QL Games still available commercially
and a wealth of public domain software available from the Sinclair QL Homepage
As for expansion options - the most commonly required ones are disk and memory interfaces - there were quite a lot of these produced, but ideally you want a Miracle Systems Trump Card which added 768K memory, and a disk interface. Later interfaces such as the Gold Card and Super Gold Card offered memory expansion up to 4MB and a much faster processor, and even allowed the QLs to use ED disk drives (3.2MB) as a mini-hard disk.
There were all sorts of other peripherals, some home made, others more commercial, including hard disk interfaces, a new motherboard (the Aurora) which offered 256 colours and high resolution displays, I/O interfaces, EPROM programmers, video digitisers and speech modules for example.
There are also a number of QL emulators for various platforms, with the Windows based QPC2 probably the most common emulator, followed by Q-emuLator (Windows and MAC).
There is still a QL magazine (QL Today) and even a QL user group (QUANTA) which was first set up in 1983.
Plenty of information for you to absorb and read up on - but if you want to know anything else, just holler.