On your last question, it depends if you're after 320-330bhp or happy with 280bhp and slightly better spool from the TD04?
Fuel pump is fairly simple, just a bit fiddly getting the cover back on with the rubber gasket nice and flat. Done 3 fuel pump swaps on newages now and I'm by no means a mechanic!
For the exhaust parts, if there are seized bolts sometimes its just easier to have the car up in the air to get proper leverage on them. It can be a right pain struggling underneath with the car on axle stands trying to loose old uppipe bolts etc