No offence intended but when you need to ask that sort of question you probably aren't competent enough or experienced enough to tackle the job or make the required decisions - whether or not machining is needed, whether things are clean enough, etc...
Replacing a head gasket is rarely straightforward, is never a quick process if done correctly and needs a high degree of skill and experience for the finished job to be long lasting and reliable.
There is hardly scope to list the procedure here and much of the process is largely intuitive based on experience - something that is better demonstrated and difficult to write.
Answers & Comments
No offence intended but when you need to ask that sort of question you probably aren't competent enough or experienced enough to tackle the job or make the required decisions - whether or not machining is needed, whether things are clean enough, etc...
Replacing a head gasket is rarely straightforward, is never a quick process if done correctly and needs a high degree of skill and experience for the finished job to be long lasting and reliable.
There is hardly scope to list the procedure here and much of the process is largely intuitive based on experience - something that is better demonstrated and difficult to write.