I'd say yes, you should change the strings. Some steel strings last a year (maybe a year and a half if it's not played much).  Pretty much all brands will be pretty dead after 4. (And if they're synthetic, the lifespan is considerably shorter.)

Re the bridge, my first thought would be, change it if it needs it, otherwise don't. If it's warped or bent, then it needs to be changed. If not, I'd say change it only if you think it needs a better quality one. You might want to post a couple or three pictures of the current bridge, to get the opinion of someone better qualified. (I'm fairly new to all this, and no luthier.)