Inverters and converters are not terribly complicated to repair. However, cost is dependent on what failed. If you have a friend or neighbor that has electronics troubleshooting experience, they can probably take a look at it and figure out what component(s) have failed. Then, you can make a more knowledgeable decision on how to proceed.
Unfortunately, with modern electronics, it is often cheaper to replace with newer and better devices than to repair, primarily due to the cost of labor. However, your friend or neighbor may also be able to fix it, perhaps for a beer or two (or other beverage of choice); preferably AFTER the repairs are done.