possible blown Head Gasket

[2Fast2Furious]

POSITIVES:

* car doesn't have milky substance in oil cap
* temperature guage reads fine
* coolant is still at full level
* engine sounds good

NEGATIVES:

* there is a smell from under hood, I thought it was oil, I can't destingish if its the sweet coolant smell
* there is a substantial lose of power (very sluggish)
* idle's very roughly and engine easily dies off in idle
* some white smoke from exhaust
*coolant is grey but not sludge (though I heard this can be due to red and blue coolants being mixed, guess a coolant change is in order)

My local Toyota garage can't take her in until Monday next, I have already drove her alot and don't want to touch her again in fear of fecking the engine.

Could the lose of power just be spark plug problem?
Could the grey coolant simply be a Water Pump seal leak problem?

If I do need new Head Gasket should I just go for stock part? Are they aluminium?

Would it be worth going with:

ARP head studs and a 2mm thick piece from HKS and fitted with 1mm oversized valves, and stock cams fitted with AEM cam gears. (lol, not sure what this is all about but if its good I will pay)