I've done it to my Sheridan and 392pa. It's not hard to do at all and it might keep your barrel from separating. Supposedly if it gets bad enough it effects accuracy.
If you haven't already done it, get some Secret Sauce. Use it to keep your vintage pumper working/shooting for many years to come. A little goes a very long way.http://www.mac1airgunshop.com/secret-sauce-10-oz-refill-size-p/m1ss6oz.htmFrom Mac-1's own site:Lubrication: EVERY TIME YOU TAKE IT OUT TO USE IT YOU WANT TO MAKE SURE THAT THE LEVER PIVOTS ARE MOIST WITH SECRET SAUCE. You'll get a 1.75oz bottle of Secret Sauce with every Steroid purchased or upgraded.Don't overdo it, a few drops at the front pivot & rivet is all you need on those two. The pivot that connects the lever link to the piston end that guides it is a porous piece of steel. Put 6-8 drops of Secret Sauce on that pivot as the guide end of the piston acts as a storage of oil so a film is laid down on the tube each pump stroke. All else will get taken care of by blow through.Never put lubricant in the air hole. Do NOT use firearm cleaning solvents or lubricants anywhere on the gun. Rem Oil & Barricade provide a good external wipe down oil. I use Rem Oil as it has proven to be one of the best rust inhibitors. Don't put your guns away with salty paw prints all over it. When you take it back out the steel parts will be all rusty.
Trash that Pellgun oil. Over a period of time it crusts up inside the internals.
Secret sauce is hydraulic oil.
Here are instructions for adding a peep sight.http://anotherairgunblog.blogspot.com/2013/01/mounting-williams-peep-sight-on-sheridan.html