Surface Rust is easily removed, by putting heavy motor oil on the metal, and then lightly burnishing the rust off with either a wood stick, or fine steel wool, also dipped in the oil. ( HINT: Rust is actually : Flowers of rust, when it comes to iron oxide. The " surface rust we talk about here, finding such in the bores of the gunbarrels, is actually microscopic flowers or oxide that are sitting up on the top of the metal. Your rust on the outside of the barrel will stick up further, and can be seen in good light with the naked eye. Burnishing the surface knocks these flowers off. the heavy oil keeps them from scratching the surface around the flowers. )
Then clean the barrel with alcohol, to remove all oil, and fingerprints, and heat the barrel up with a propane torch until water sizzle off the barrel. Apply any cold blue compound you have to the barrel while its hot, and it will burn the finish to a similar color as the factory color. Cool the barrel, and rinse off the acids, and residue from the barrel. Dry it. Clean it again with alcohol. Heat it again, and this time spray it with WD40 or any other good gun oil. The oil will smoke, as it cools the barrel. Don't breath in the fumes. Oil it until the oil stays on the blued spot.
Let the barrel cool over several hours to room temperature. You should have a barrel that looks as good as it did when it came from the factory, save, perhaps a few minute pin holes where the oxide removed metal. They are so small that unless you know they are there, and what caused them, most people don't even notice them.
Value of a used LH Renegade? It should be worth at least $300.00. Perhaps more to the right shooter. Start the price in the $400-$450 price range, and come down to make your deal.
Look at the cost of new rifles from T/C. I don't think they are making the renegade any longer, but when you see the prices for new guns, buying a well made rifle from the company, with its Lifetime warranty makes it worth a lot more than many other makes of rifles, IMHO.