Trying to fix smoke on Legacy Camelback.

First of all, please provide a product number for us to assist you easier with this repair.

Second... If you're not getting any resistance from the heating element, either from the corresponding pins of the J connector or on the leads of the heating element. There's a high chance there is a break in that nichrome wire of the heating element. Yes it is fully possible to replace just the heating element if it went bad, I have done this to 3 smoke units before and brought them back to full working order.

You will need a high heat soldering iron, some solder (leaded or unleaded), pliers (to hold onto the heating element without burning your fingers while trying to desolder it). Solder wick (to clear the old solder from the pads), and a new heating element. You are lucky since Lionel now sells the heating elements pre-bent to the right shapefor their smoke units.

Since you have gone through this much disassembly to get to the smoke unit, you might as well refresh the batting with new stuff and replace the other heating element. Just so you don't have to be back in there for a while. Also, whenever you get to reassembling the smoke unit. Check for a 1/16" gap between the heating element and the diode. The diode is used for measuring the temperature of the heating element to keep it at optimal temperature

Before you break out the soldering iron, break out the ohmmeter.  Check if the elements are near 8 ohms, then inspect the wiring from the smoke unit to the LCP main board.