3. I want to remove the 'CATEGORIES' from the left sidebar.

You can adjust what appears in the left sidebar using the Appearance → Widgets page in your blog dashboard. If you get stuck, check out this help page about widgets: http://en.support.wordpress.com/widgets/

2. I want to change the background of the site to black while keeping the background colour of the main body white.

This should work:

body.custom-background {
	background-color: black;
}
#page {
	background-color: white;
}

Note that you can also do this using the "Colors & Backgrounds" color palettes when you go to the Themes page and click the Customize button. Check out this help page to see details and examples: http://en.support.wordpress.com/custom-design/custom-colors/

1. I want to remove the date from the text on the featured image slider on the home page.

I see you figured this out using the following CSS. Nice work!

.entry-meta {
	display: none
}

How do I go about getting staff support, it's quite urgent..

Staff provide CSS editing support in accord with the the earliest dates on the threads in this CSS Forum.

I've managed to find the CSS code to remove the date from the text on the featured image slider on the home page. But if anyone can help with changing the background of the site to black while keeping the background colour of the main body white and removing the 'CATEGORIES' from the left sidebar, that would be very much appreciated.

Many thanks.

I am completely new to WP so please excuse my ignorance.
I am using the Oxygen Theme on this site:
http://britishandmuslim.wordpress.com

I've got three problems:
1. I want to remove the date from the text on the featured image slider on the home page.
2. I want to change the background of the site to black while keeping the background colour of the main body white.
3. I want to remove the 'CATEGORIES' from the left sidebar.

I've purchased the Custom Design upgrade if that helps, but not sure how to edit the CSS or if I need to...

Any help much appreciated..