Sourcing a head!?

[Cuz]

Ok,
i have the feeling i have a small head gasket leak water to oil, so i'm taking this oppertunity upgrade my head.

A few questions: How easy is a tx big valve head to find (I'm in melb)?

There is few do it yourself wreckers around, should i try them? Where else can i try

What else should i check other than the actual head surface with a straight edge?

How do you check the cam tunnel?

What other dodgy stuff should i look out for (Water jackets, cracks etc)?

Where is good place in melb to get gem head work done and what is the least expensive way to get a bit more out of the head?

I know shaving is relativley inexpensive to up the compression, how good/expensive is porting and polishing?

[ONLYA4]

You could shave the head and get the valves holes re-drilled and put in bigger valves. (im pretty sure you can)

Porting and polishing is a few hundred dollars and is a significant increase in power if done right. If its done right ya can tell but if not then you can barely tell and its not worth it. So go to somewhere that comes highly recommended by someone.