Greetings tommy burel and welcome aboard.
I'm a little confused: I think of a 1911 as being a version of the Browning designed .45 automatic pistol. I'm not aware of a model 1911sl shotgun. Winchester made a very popular shotgun that was introduced in 1912. It was originally known as the Model 1912 but as its fame increased the name was shortened to simply Model 12. I'll assume that's what you mean.
The Model 12, being a pump action gun, doesn't have a recoil spring; but, it does have a large coil spring in the magazine tube that feeds the ammo. Replacement magazine springs are cheap and readily available. As for the wood dowel (or "plug"), it serves to limit the magazine's capacity to comply with some hunting regulations. The gun will function fine without the plug; however, if you are hunting without a plug when it is required, the penalties may be severe.
Model 12's value can vary drastically, a gun could be a rare target model worth several thousand dollars or some farmer's daily beater suitable only as a parts donor. Some pics and specifics about your gun will help in estimating its value.