want to start a tank but need some help!!

Hey. I want to convert my 45 gallon freshwater tank to a saltwater tank but i need some advice on the proper equiptment. I was told that you need to have a filter, protein skimmer, and a set of expensive lights. I saw a filter with a built in protein skimmer for $90 and wanted to know if it was any good. it was a skilter i belive. if any one could give me any help it would be much obliged.