Audiqv8

Get a code reader and clear the codes and see if the transmission shift normal. If it runs normal until the check engine light popup then I would suspect that the P330 is causing your shift problems, preventing the torque converter from locking up. You can decide to repair or sell the car. Removing the head to fix the dead cylinder the knock sensors can be replaced since the intake manifold will have to be remove to replace the cylinder head or replace the valves. If it was my car I would have the head inspected by a machine shop and ask for a cost to repair it including replacing all the valve stem oil seal and valve guides if needed.