Nice bike OP, if I may suggest before you take it apart to clean it take lots of pictures of how things go together, how the brake and shift cables run how the seat clamp bolt goes in etc it can help a lot on reassembly and if you don't do it you may regret it later, ask me how I know . Have fun, take it slow, for sure deal with rust but I think you can deal with the rusty chrome area, touch it up with some silver nail polish to protect the bare metal you will have after you remove the rust and do the other maintenance -ride it, see how you like it, does it still fit? and then consider how to do a more permanent fix to the chrome, I have not done it but I understand re-chroming can be pricey.