If that's a currently in-production model, or even a relatively recently discontinued one for which spare parts are still available, I'm sure Canon can fix it.
Just be aware that a factory repair facility like Canon's will replace any and all damaged parts modularly, so the cost can run rather high.
The obvious damage - the filter ring dent - is actually the least of your worries. Over the years I've straightened out many of those with simple, non-metallic tools I've made myself. I first used hole saws of various sizes to make hardwood "anvils" to rest lenses of various diameters in, and then used a variety of plastic and wooden objects (hardwood sticks, toothbrush handles, etc.) to make "stakes" that can be used to get in there and push the filter ring back into proper shape. Metal will want to return to shape for the large part and this type of straightening repair can usually be made fully usable, though there might be some cosmetic damage still evident. Sometimes I can just "press" softer and thinner metals such as aluminum back into shape by hand. Other times some gentle and careful "encouragement" tapping on the stake with a small hammer is necessary. Alternatively, there are special pliers and vices available to repair filter ring dents, some of which aren't cheap. But I've found the results with those no more satisfactory than what I can get with the tools I've made myself. In fact, often a metal tool ends up doing more cosmetic damage, scratching the lens' finish (touch up is possible, but never as good and durable as the original finish).
At any rate, the filter dent is rather easily fixed. Canon will just replace that part of the lens barrel. An independent repairer would more likely just straighten it at lower cost, unless you insisted on replacement (in which case they'd have to acquire the part, too).
Actually, more of concern is internal damage, especially since you mention that focus accuracy now seems off. It might be as simple as recalibrating the lens. Or it could be as complex as broken parts or a decentered element or group of elements that need repair and/or replacement. Some disassembly will be required for that and at a minimum there will be some labor charges.
Send to Canon, if you prefer. You can be sure that their repairs will be good and they'll warrant their work, too. But an independent repairer might be able to fix it well, too. Maybe at lower cost. There are still some good repair techs around. If the lens is an older one, discontinued and with the replacement parts they deem necessary unavailable, Canon may not be able to repair it. In that case you may have no choice but to have an independent repair tech deal with it.