If you do decide to do them it’s a good idea to clean all the old congealed grease and dust etc. which actually will have set like tarmac in the rails. The same applies to the rollers on the hangers if you are reusing them (you also need to check for broken / jammed ones and replace them). Cleaning is a disgusting job but some nice new clear grease on them after and the way they work is transformed. Like Franglais I am assuming you mean the PVC 
side curtains, not some nice chintzy frilly ones for the cab