Though you certainly don’t have to install your own OS – you can buy SD cards ready installed http://thepihut.com/products/raspbian-preinstalled-sd-card . That’s about the only bit I can imagine is particularly daunting, and is what I’d recommend for anybody new to this – the rest is just the same plugging together as you have to do with a Kano anyway which they make a selling point of.
So the shopping list is:
RPi
Micro SD card as above
RPi case
Micro USB power supply (I’m guessing most of us already have one or many of these – I now have too many and my RPi is plugged into a mains socket with USB outputs).
USB Wifi dongle (it used to be tricky, but even the awkward one I have which I had to compile stuff for when I got it now works plug and play)
USB keyboard
USB mouse
HDMI cable for TV
I think that’s it – I don’t see any need for a speaker as the sound goes through the HDMI cable to the TV. I could give you a list of specific items, but you’re all grown ups capable of shopping for what is a fairly generic set of things.