Hi, all. Need some tips on soldering and unsoldering MOSFETs.

On unsoldering (bad) ones: They are of the types with fins soldered on to
the surface of the board. Do I just apply heat to the top of the fin (D),
and then lift the MOSFET to an upright position before unsoldering its two
outer legs (G & S)?

On soldering good ones: Are there any heat precaution when soldering a new
MOSFET? Should I clamp the top of MOSFET to a heat sink before applying heat
to its legs? Would a 40W iron be too hot for the job for an amateur hand?

Thanks
Al-U