They way I read it you are trying to remove the rear insert first.
Yes, use a steel fieldpoint screwed into the rear insert and heat it as needed with a lighter or torch on low, use just enough heat to melt the rear insert glue, you must judge in steps just how much heat is required, work in small steps just add more heat if required till glue adhesion softens. Go slow and try pulling the insert out.
Use vise grips to twist and pull the factory aluminum insert out.
If you have a round mini file you can sand out any residual glue from the shaft end, sandpaper around a drill bit will work too. Clean with alcohol when done.
Insert the Lumenok with firm thumb pressure. If too much resistance in noticed just use a sharp blade and shave one of the four slightly raised edges on the lower Lumenok being careful not to nick one of the two very small metal contact points at the junction between the upper and lower part of the Lumenok.
Come back with any questions that you may have.
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