For light rust on the chrome, use ultra fine (0000) steel wool and very lightly polish it until the rust is gone. There is not much that you can do about scratched decals. You can either find a custom decal shop to make you a set and then strip and repaint the bike, and put on the new decals. Or if you are good with a paint brush, you can paint in the missing areas. If they are very slight, it may be best just to touch up the paint to prevent it from rusting.
You should do a complete overhaul of hubs, BB, and head set. You can use any degreaser or even Simple Green to clean them. I usually use a 1-1 solution of Simple Green and water to clean bearings and races. Just be sure to dry them after cleaning them so that they don't develop surface rust.
Measure the inside diameter of your seat tube and order a replacement seat post on eBay. Look for a Shimano 105 Seat Post if you are a purist like me. Otherwise, any seat post that fits should work just fine.
Gently work the brake hoods off of the brake lever assemblies. Remember how you got them off. Soak the hoods in pure Simple Green for a day or two, then scrub them with a tooth brush. One with stiff bristles is preferable, but a medium will work. It will just take longer. After you have it clean, rinse off the Simple Green and put them back on the brake lever assemblies. It is easier to put them back on if you lubricate the hoods with alcohol. Or you can use hairspray, but you have to get the hoods back on and positioned before the hairspray dries or you will have to dunk the entire lever assembly in alcohol to wash off the hairspray.
If I were you, I would replace the cables with ones that have either a black casing or yellow casing. White just doesn't look good on a yellow bike.
Buy your saddle at your LBS. They can be had cheaper on line, but they often cannot be swapped out if it doesn't work out for you. No backsides are the same, and a saddle that works for one person may not work for another. A saddle is probably the most personal component on the bike. Most bike shops have a program where you can purchase a saddle, and if it doesn't work for you, you can bring it back and trade it for credit on a different saddle to try. Most shops have this program or one similar so you will want to ask them what their particular program entails. There may be variations on the time that you have to try the saddle or there may be a restocking charge deducted from your store credit.
Good Luck and don't hesitate to ask any questions that you might have.
