2004 holden astra ts

Hi, I am in Australia and have just bought a very nice Astra, it does need a couple of things doing to it.
1.. the strut top mounts need replacing, does anyone know if the whole strut has to come out for this?
2. the speedo seems to have a mind of its own, it works ok then stops, works fine for the next few trips and then just doesn`t work again for a while. Someone suggested a speedo sensor might be the fault, and says the sensor is behind the lhs disc brake. Anyone know about these items.
Thanks