If you do replace them you might need to change the cluster. If you need to change the cluster then your clocks will be out
There are ways around this, not easy ways, but ways nonetheless. For instance, if you have VAG-COM you can get somebody to tell you what speed you're doing while you pop the needle back on, or you can do something similar via the hidden menus on the climate display. It's a bit Blue Peter and you need somewhere safe away from a busy road (luckily I live next to a forest!) but it's fairly straight forward
Same applies to the revs. Wait until the car is up to temperature so the idle is consistent, monitor it in VAG-COM and pop the needle back on. Temp is the same. Petrol is easy, fill it to the brim and pop the needle on.
However... if you're really clever, you'll be able to get the dials on without removing the needle. Some dial kits sit over the top of the stock dials so you can slide the needles through the holes in the new dials. Tricky, but not so hard it's not worth trying