Lee, wake the fuck up and read this properly:
First off, no, you don't need a monitor. A telly will do, but it'll be slightly fuzzy. This won't really matter much in games, but you'll definitely notice it on the desktop as the icons will be a bit blurry. Secondly, you'll probably have a bit of input lag. This is the time between you moving your mouse and the cursor on the screen actually moving. In movies and TV shows and stuff, this doesn't matter but in gaming you'll notice it. HOWEVER! This won't be an issue until you're playing competitive games on a reasonable level. For the level of gaming we play, you should be fine. Also, most tellies have a "gaming mode" which effectively turns off all the fancy schmancy image effects and pumps out the image as quick as it can. This doesn't eliminate input lag, but reduces it significantly.
Secondly, the pc part picker he used is called.... wait for it... PC PART PICKER! You can spend hours on that fiddling, tweaking, etc. It'll show you the current prices for most hardware components at various retailers, but it still helps to shop around yourself and see if you can bag deals. Even if the price is the same, some places will chuck in a free game or whatever. Also, ALWAYS check Topcashback and Quidco.
Another site which is excellent is logical increments which gives you a rough idea of how certain components compare to others. If however you just want to compare performance between two graphics cards or CPUs, then use GPUBoss or CPUBoss. CPUBenchmark is also pretty handy. Keep in mind however that although one game might get 200FPS on your system, the next game might only manage 30. This is due to the load, the way games are coded, how much is going on at once and how well the game is optimized.
Lemme know if you need anything else