trueblue +10 You just need to clean up the starter just new brushes will not do. Forget the battery
If you are not up to it where you live will have a ton of starter rebuild shops they will clean it up check bearing or bushing and have it back in a day or two. Then you can be doing other things. But take it off for them. Hit the yellow pages. Now if you want to do it. On larger starters I use a hacksaw blade trimmed down on a bench grinder. These are small and a sharp pick works good to clean out the grooves a big rubber eraser works to shine everything up and some brake clean to wash it off. Then you have to see how much it wobbles in the old end caps. Then check it electrically The shop has everything and can do it faster.
EDIT Looks like you posted while I was typing.
Ken