Blackie,
Here are my recommendations to take care of your black Yukon:
1. Go to Target and purchase a pack of microfiber towels (eight per pack for about $7), a box of Meguiars Claybar (about $15) and the red bottle of Meguiars cleaner wax (about $7).
2. Thoroughly wash your vehicle using a 1/4 cup of Joy dishwashing liquid mixed with a full bucket of water. Joy dishwashing liquid will remove any contaminants or anything else that is on your paint....including any previous wax that was applied.
3. Following the directions on the Claybar using the spray bottle that comes in the box along with the actual claybar. Take your time on this part of the process. It's time consuming but you will be amazed when you see the contaminants that the claybar removes. It will be a clean beige color when you start but not when you are done. CAUTION: If you drop the claybar on the pavement, throw it away (the package should come with two claybars). These things pick up anything and you will severely scratch your paint if you accidentally pick up any pebbles or something off the ground. Also, remove any rings or jewelry on your hands/wrists. Sometimes the claybar will hit a dry spot and a ring will scratch your paint. Don't be afraid to use the spray liberally. When it dries, remove the claybar residue with a microfiber towel.
4. Following the directions on the cleaner wax. Do not over apply as it just is not necessary. Remove the wax with a separate microfiber towel (not the one you used removing the claybar).
Plan to spend about 4-6 hours in this process. Your black Yuke is going to look awesome. However, you've just purchased the prettiest color when it's clean and the ugliest color when it's dirty. I've owned two black vehicles in my life and I said "never again" when I sold both of 'em. Will I ever own another black vehicle? Yeah, but I know what it takes to keep it up to my standards and it's a LOT of work.
There is an excellent video on youtube.com on the claybar process. Here is the link:
http://www.youtube.com/watch?v=yfEfLGL59GI
Good Luck....and post some photos for us!
Sothpaw62