If the symptoms are those described above, the best thing to do is to immediately replace the seal: it is a vital element for engine sealing, neglecting wear can cause irreparable damage. You can replace the seal yourself, but it is delicate and quite difficult, requiring mechanical experience and excellent leadership.
Just to be able to check the damage is to disassemble a large number of engine components and remember, the correct positions of all the elements is essential, it is recommended to do so only for those who are really expert.
After removing everything, and by separating the head from the cylinders, it is still necessary to go through a repair workshop and make changes to the valve tips.
Willing to engage in the assembly of a new grip will have to use specific tools such as the torque switch and you also need to do very delicate operations such as cleaning the coolant if it is wrong, it can burn the gasket again .
In conclusion, if you want to install on your own print, organs with all the tools and very detailed manuals; Otherwise, it may not be a bad idea to make it directly in the service of your trust.