Slow down Grasshopper. Pretty much every new collector wants to do this. But it is not always a good idea. A polish isn't necessary to preserve your sword; as long as any active red rust is stabilized, your sword will be just fine in its old polish with proper maintenance. Sharpening = polishing and polishing removes steel from the blade and too many polishes remove enough steel that the blade's core steel starts to show through, a serious and ugly defect. Beginners often don't know how to properly care for a blade in polish. A new polish is easily scratched or even rust spotted and before you know it, the blade needs a polish again. Old scabbards can contain grit that can scratch a newly polished sword, or talking over a blade can lead to tiny droplets of moisture on the blade which turn into rust spots very fast.
Beginners often make the mistake of having their sword polished by an improperly trained polisher, which can irreparably damage the sword. Also,remember that not all swords are worthy of a polish: retempered, tired (core steel showing), and badly defected swords will not be worth the cost of polish. Low to mediocre grade swords are often worth less than the cost of polish. There are many periods in Japanese history where swords were produced as fast as possible, with less care about aesthetics and more thought about producing functional weapons. It is a fact that age doesn't necessarily mean value. In these cases your money would be better spent on a more worthy sword (or books). Learning to distinguish between mass produced utilitarian blades and those worthy of polishing is a huge part of your studies, and this is where the advice of knowledgeable collectors is invaluable. Spending $2500 on a polish for a sword that will be worth $1500 afterwards only makes sense if the sword has sentimental value. Otherwise, the money is better spent on upgrading. Having koshirae (mounts) made for a sword is also a common desire of new collectors. While this will do no damage to the sword if done by a professional, it can put a serious dent in your wallet. When the time comes to sell (and it will, unless you plan to be buried with your sword) you will be lucky to recoup half of what you invest in koshirae. Other collectors want original "Samurai" koshirae, not something you put together. Rather than jumping in with polish and/or koshirae, you would be smart to take your time to study and learn. With experience you will be able to make informed decisions and spend your money more wisely. Also, your tastes will change. A few years from now you'll be glad you don't have way too much invested in something you want to sell.
•Who should I have polish my sword and how much can I expect to spend? In the west, especially in the United States, there are many polishers to choose from. I can count on one hand the number of polishers outside of Japan who have proper training. A poorly done polish can do significant damage to a sword, both artistically and monetarily. Put another way, the most expensive polish is often the one that costs the least. We can not over stress this point: Don't give your sword to an amateur polisher.
•How do you know if a polisher has proper training? Ask experienced collectors (here on NMB, for example) who they'd recommend. If the polisher lives outside of Japan and he advertises his services on ebay or someplace similar, you don't necessarily want him to touch your sword; the true polishers have more than enough work without advertising.
•What will this cost? Prices vary with the condition of the sword to be polished but a good rue of thumb is $100-120 per inch of cutting edge. You will also need shira-saya (plain wooden mounts) and possibly a new habaki. You won't be putting a newly polished blade back in its old mounts because the polish can be scratched by any grit that found its way inside the saya over the centuries. Shira-saya can cost a few hundred dollars and habaki, if necessary, at least $200 more. This isn't inexpensive, which is why you need to make sure your sword is worth the expense. A properly trained polisher will be glad to look at your sword and give you good advice.
•How do I know if my sword is worthy of a polish? If you have been advised by knowledgeable collectors or other experts that your sword might possibly be worth restoring, one way to find out for sure that doesn't cost an arm and a leg is to have a professional polisher open a "window" on your blade. This is a small area of the sword that is polished to see the actual workmanship, hada, hamon and hataraki and see if the blade exhibits quality workmanship. Most polishers will do a window or at least look at your blade and give you advice. The other way is to find a sword study group or sword show near you and get the advice of as many advanced collectors as possible. Online opinions are at the bottom of the reliability scale, as there is only a limited amount that can be determined from pictures, but if from advanced collectors, is better than no advice at all. The key is to ask, ask, ask...before doing. Then take some more time and think it over before you make up your mind.