MG, powerfiat take around 3 hrs iirc for a cambelt swap, so add in another hour for the cam position sensor for pro's that work on tha engine day in day out! a non hgt experienced mech i would expect to take circa 6 hrs or so
you can do it yourself if your competent with the spanners, but it wont be easy. you will need a full cambelt kit, water pump, aux belts and tensioners aswell as the cam position sensor and get your hands on some cam locking tools aswell.
ill be undertaking a cambelt and clutch change myself at some point in the not too distant future, but i have the benefit of my mates garage (one he runs rather than attached to his house..) to work in with a massive selection of tools, ramps etc etc (oh and cost price on parts too)
to do it you will need to move the engine over to the pass side as much as possible, remove the cambelt (once you have fitted the cam locking tools) then remove the timing pulley for the exhaust cam, thats where the ensor hides on the hgt) and then refit your new bits n bobs
Andy_sx