Missing the services really clouds the issue, as you don't know if the problem might have been picked up before it became a major issue. There's not a lot you can do, you need to find an engine and get your car going. You would be unlucky for it to happen again. You could also try to convince Hyundai to come to the party with part payment for the repairs, which might help alleviate the financial burden for you.

I would say don't sell it; fix it. It will be very hard to sell when it needs a new engine, so I would take it to a wrecker specializing in Hyundais and they should have a suitable replacement they could install for you. If you sell as it is you will take a bath on it.

Using oil is not necessarily a problem, it depends on how much oil it is using. Likewise the colour is not necessarily indicative of a problem; oil usually goes black after it's been run through the engine for a short period of time. If it is using a lot of oil take it to a Hyundai dealer and have it checked. There is nothing inherently wrong with Hyundai engines, and at 88,000 km and four years old it should be covered by the warranty.