You can probably get away with just cleaning the carbs. You will know for sure once you get into them anyways. The tank is probably all messed up, +1 on the Kreem advice.
Once you clean the carbs and the tank and you get the thing running it might be worth it to have your local shop do the balancing and valves. They arent outrageously difficult jobs, but they require some fairly expensive tools that dont have a lot of applications, and the shop shouldnt charge you too much to do it for you. If you find some local bike nuts they will probably loan them to you (not to mention showing you what to do with them).
If i were you, i would start with the most simple solution first, clean the carbs on the bike and put in some fresh gas and see if it works, you might be suprised. The hardest lesson I have learned with old/wornout/high mileage bikes is that there will *always* be something on the list that needs to be fixed. Spending more time than you have to working on something that isnt broken will make it all the more frustrating when something else goes wrong.
It should go without saying that you absolutely must make sure that the chain, sprockets, bearings, brakes, and tires are in good running order before you ride it. Take a good close look at the tires, old tires might look good with deep treads, but if they have gone hard with age they can slip like crazy. Those things are the 1st priority on a bike because they can get you hurt pretty damn quick.
