Another option is Novus to remove some of the finer scratches you will still need to wet sand the areas you want to repair but novus does a good job.
With what rich said yes it is a huge commitment but salt water is so easy now its pretty much dummy proof. The main thing you will spend money on is the lighting that is a huge part of it if you want to do corals. But if you are handy with a soldering gun you can wire up your own LED's for really cheap. Some people swear by them and others like me are not really sold on them for coral growth and lively hood.
A protein skimmer is not really necessary depending on your tank. Up to a 50 gallon or so you can simply change the water weekly. As tanks get larger it gets less and less realistic to maintain the water by water change alone. A 120 needing a 20-30% water change a week is quickly going to cost more in salt than a skimmer. Another option to replace a skimmer is making a turf scrubber but that depends on you and the size of your tank.
Corals depending on what you are looking at can cost you a lot of money right now the most expensive coral I have in the store is more than likely a very large putat and a large Australian prism brain that is neon green with bright yellow eyes. But if you can find a good lfs that has coral you can pick up frags for cheap I sell mushrooms for 10-20 bucks depending on the size same with leathers. Once you start getting into some of the harder to keep corals like sps and some brains that's where its going to cost you money.
Fish will be the same as coral some fish are very hardy like and of your Pseudochromis, Clowns, Damsels, Chromis, some cardinals, and hawkfish to name a few. Then when you get into some of your more deleciate fish like some butterflys, angelfish, and tangs you will need a UV sterilizer. Some are rather cheap and others really expensive but in the long run they will help with green water and parasites. I actually plan on putting on on my tank soon.
Don't let the prices of things discourage you on doing saltwater there are tons of outlets you can look for peoples used stuff like Michigan reefer and craigslist to name a few. If you choose to do salt feel free to ask me anything on it. I just lost interest in it since I am around it daily. If you ever want to make a trip up to the store let me know Saturdays are the best time for me since Im not to busy with other stuff.
Sorry for taking it off topic I could of pm'ed you
