Canon Squeal

Question

I recently bought a Canon A1 35mm film camera off eBay. The outside is in amazing condition but the seller did not use the camera for a very long time so it had not been lubricated. I put a new battery in it and pressed the shutter release button and heard a squeal and the shutter was staying open way too long. I'm not experienced enough to trust lubricating it myself and wanted to know if you did this in your store and if you could give me an estimate on how much it would cost. I'm just afraid of spending more having it cleaned up and lubricated than I did on the camera itself. I bought it for only $100. Thank you!