Heads?

I appear to be leaking oil through my head gasket so i'm setting up to replace it soon. Thinking about taking all the time to undo the head has me wondering:
A) is there anything performance-wise that i could do to the head while its off?
B) is there anything i could install or do to the intake manifold while it's off or the throttle body while i'm at it?
C) is there any other engine that i could do a head swap with? a friend of mine is doing a vtech head swap on his civic and it seems so easy to get so much more power, especially when i need to take the head off as it is... any other engines i could do a head swap with when i have a 99 sentra gxe with a GA16DE?

1)3 angle valve cut, JWT camshafts(i think they have GA16 cams...), find someplace with dual valve springs, titanium retainers, and after that you can flash your ecu to raise the redline a little

2)if you trust yourself you can hand-port and polish the runners on the manifold and the ports in the head, or take them to a machine shop and have it done.

3)most nissan heads are very similar in flow characteristics, and they dont have cheap vtec heads. im not sure if a sr16ve head would work or not, but it is very expensive and requires LOTS of modifications, especially electrical. that is even if it works in the first place

1) what is the three angle valve cut?
2) How exactly do you port and polish and what would you be porting and polishing? any links to pics?

1) Port & polishing is best left to the professionals. It involves taking metal out of your cylinder head ports to smooth out the flow of air(basically, giving a knife edge) Taking too much out of one cylinder and you have a fucked cylinder head.
2) 3 angle valve job, involves optimising the air flow characteristics of the engine thru the valves, promoting swirling of the gas mixture.
3) SR16VE head swap is a no go(SR motors are alloy block with different bore and cylinder spacing) but fit a thin metal head gasket and bump up your compression ratio for some more power.