^ Can you re-word that? Seems thats its missing 'do the' after the 'I' but still doesn't make sense to me.
Take the heater core and tubes out from behind the dash to work on it.
Remove the o-rings and clips.
Remove all moisture possible prior to heating.
Prep the tubes by lightly sanding off oxidation and applying flux.
Fit and clock the tubes the appropriate direction.
Heat the tubes (not the solder or seam) and melt the solder into the seam with the heat of the pipe.
Ensure that you didn't make the solder run with too much heat, no gaps allowed.
Let cool before disturbing.
Wipe off excess flux with a rag.
If there are gaps, perform a local solder by applying flux at the gap to fill it and use light heat on the tube location of the gap. Hold the solder at the gap until the heat of the pipe takes it in and remove heat immediately.
Let cool then wipe.
Install
Do not use too much heat and don't concentrate it too much near the core or that'll have to be re-done.
Obviously this will be hot, there is open flame, and the hot solder/flux will drip.
Do much thinking ahead before starting, to make the job easier.
-Dave
EDIT:
NOOO!! Avoid directly heating the core at all costs or this will get out of hand