Desoldering a TO-220 MOSFET from a plated through-hole board with SMD complications
If possible, I would recommend removing the damaged through-hole transistor by cutting its leads above the board surface, then simply trim the leads of the new one to where you can install it by simply placing them on the existing solder pools &amp; melting the existing solder (possibly with adding a very slight amount).

This may not be the "prettiest" way to effect the repair, but since you seem to not be very experienced with soldering on PCBs with SMD devices (and don't necessarily have great SMD soldering equipment), it's probably very much the safest.