First of all the diesel noise could be your variator, but seeing as you will need to change that you may aswell change the cambelt setup and waterpump too. The cambelt should be changed every 36k miles and shouldnt be left any longer than that, if your cambelt breaks then thats it, possible engine rebuild. the cost at an Alfa garage for such including the variator would be about £600 or a bit more than that. At an independant specialst you maybe get lucky and get it done for about £400
As for the oil leak, from your video that seems like its your rocker gasket, thats not so bad to change and if you did it yourself the gasket and sealant would be about £20
If youre getting the cambelt and variator changed then the garage will also replace the rocker gasket (if thats the problem) as they have to take the rocker cover off anyway.
Also oil and water must be checked once a week, you cant let the oil run low in these cars as it destroys the engine. These cars generally like to drink oil so definately keep an eye on it.
WOOF BARK DONKEY!