Overheating, leaks, and the rest... VT 98

So last week I decided to just have the car done at the garage to fit a new fuel pump. Turned out I also had a very dirty tank, a blocked injector, and a faulty coil whatever a coil is. So new coil fitted and new fuel pump fitted the car ran smoothly.

Then on Saturday we're driving along the Monash when suddenly the car rings out and the digital display said HOT. So I slow down and pull into the left lane when the temperature dial swiftly pointed back to the middle... So I carried on and in five minutes it had gone back up to hot again and was alarming before quickly pointing back to normal... What's that all about?

Also my steering fluid seems to be leaking. I refitted a hose which I thought was the main reason for the leak but turns out its not that. So I'm asking for this part, does a bottle of Stop Leak Steering do what it says its meant to do???

Cheers