Sounds like you have everything you need right here:
I found a bag with 2 yellow,one white and two red and a white in the house.
Although it was a very confusing post. But I would assume it to mean that one yellow is the digital co-ax, while a yellow, red and white are composite connections, and the other red and white are seperate stereo audio leads.
As said before, you can use a composite lead instead of a component lead - just match the ends so there is no crossfeed.
And with reference to the query about the SCART lead, if the manual says to remove it, then that's what you m ust do, so yes, connect it from the STB to the TV instead, as my previous post.
If you really think you need to go and buy a component lead, they come just as the three coloured ends - red, green and blue. You usually buy the audio leads separately, as most people (including you, as above) already own these.
