So, I know you'll probably think I'm retarded or something, but this morning my bike felt very differently. Pedalling felt really stiff and bumpy, hard to describe. I looked at the chain and noticed that it has become very rusty (the last few days were sort of rainy).

Pic related. It's an old road bike, probably as old as I am, but I like it very much. So what I'm really asking is: How bad/urgent does this look? Do I need to buy a completely new chain or can I do something with the old one? What about the gear? I'd just do it myself as good as I can, but last time I did that I ended up in a coma for a week, so I'd kind of appreciate an opinion from someone who actually knows his shit.