You have picked up one of the finest 1/72 scale modern armor kits made. It is by far the best Abrams kit in this scale. If you are insane like I am, ExtraTech makes a photoetch detail set for this kit (EXV 72001). The PE set replaces the bustle rack, grunt rails, headlight guards, lifting hooks, GPS doors, engine grills and the track retaining rings (these are optional based on the tank you are doing).
My only gripe is that the kit comes with the early style T-156 track. This track is distinguished by its lozenge shaped track pads that give the track a chevron appearance. Later M1A1s and M1A2s use the T-158 track that have solid square track pads. During Desert Storm, T-156 was most common but T-158 was being fielded just prior to DS/DS so both could be found. Now, T-156 is just about gone and T-158 tracks are more common. Both are still found though so this is just a minor gripe.
Painting it overall desert tan is very easy. Testors Model Master makes an excellent desert sand color in both bottle and spray.
As far as weathering, a burnt umber or dark brown wash will work well. Remember, out of the three rear exhausts (between the taillights), only the center exhaust is for the engine. That grill gets dirty, grimey, and rusty. Much like your home barbecue grill. The two outer grills only blow air that cools the primary and auxillary transmission oil coolers. They stay tan and relatively clean.
The road wheel and compensating idler wheel hubs are made of a clear plastic. The oil inside is visable. Paint these a dark glossy color like black. Take a look a the bottom of a plastic bottle of cola to see what they resemble.
The outer halves of the drive sprockets (part #7) are missing the four mud holes. These are easily added with a drill and shaped with a circular file. They are oval shaped and you can see photos of them in my motor pool gallery accessible from my signature block.
I did an accurizing article on the Italeri M1, you can see some of the detail I added to that kit like the mud holes. It may help you in your detailing.
http://www.armorama.com/modules.php?op=modload&name=Sections&file=index&req=viewarticle&artid=149