Lightly push against the heater cartridge using a hex key to remove it from the hotend.

The new hotend has its own thermistor and cartridge, but it is easier to use the old ones as long as they are functional.

If the heater cartridge cannot be removed with light force, heat the block to 240 degrees celsius. From this point on, grab the block with pliers.

Remove the Phillips head screw to remove the thermistor, being very careful not to sever the thermistor wire.

You may be working with hot parts in this step. Do not touch any pieces with your bare hands.

The thermistor wires are fragile, and cannot be re-soldered. Handle with extreme caution.