Remove the terminals of the battery and all petrol hook-ups. Drain out the coolant and disconnect the ignition system fuses from the fuse box. Also take out all spark plugs which are located on top of the engine. Disconnect the air intake mechanism and the air mixing chamber i.e. carburettor along with the vacuum pipes and the coolant flow pipes.
Set the piston 1 to top dead position and slip off the timing belt. Seek guidance in setting the piston to the top dead position from your car user manual. Now remove the headers. Depending on the make and model of your car, it may be possible to remove them completely or else you will have to manoeuvre them in the space present.
Disconnect the timing covers and take out the push rods if your car has an overhead cam installed on top of the engine.
Use a spanner to take off the bolts at the top of the engine head. Loosen all the bolts till they are tight enough to be removed by bare hands. Now take all the bolts at once and note their configuration on a note book as they needs to be placed back in the exact fashion.
Remove the head of the engine, if it is not coming off easily there is no use to excessive force, just use the help of another person. Take off the old head gasket now and replace it with the new one. Make sure it fits in perfectly before putting back the engine head back on.
Now follow all the steps in the reverse order and buy a new bottle of coolant to fill in your cooling system.