Note that you can actually build a magma pump out of wood!
But there's a caveat.
The pump must be entirely above the level of the magma. So you will have to use two Z levels to do this. Magma only heats things up if the magma is on the tile of the item itself. In the case of the pump, that means that the blocked tile will never have magma on it because it is inaccessible, but the space where the dwarf can pump the magma is vulnerable.
So long as you keep that space free of magma, you'll be okay. Let it fill with magma, and the pump is doomed.
You can more dramatically illustrate this by using wooden floodgates to control magma.
So long as the floodgate is kept closed, it will be perfectly fine forever. However if you open it and magma flows into the floodgate square, then it will burst into flames and melt within seconds.
Basically, consider air to be a perfect insulator in the game. So long as magma is not actually touching an object, the object is safe. Otherwise dwarves would be bursting into flames when trying to use magma forges. And objects are only touching if they share the same square. Adjacent squares are adjacent, but those objects are not actually touching, thus are safe from magma.
Also, magma will evaporate at depths of 1 and 2, just like water. A 2 may turn into a 1, and a 1 may turn into a 0, so its just more noticeable if its at 1's.