Heater/Ventilation cable replacement

I bought a set (of 3) new heater/ventilation cables and now I'm looking for hints on how best to go about replacing the aging original cables. If the job is too involved, I'll go to a professional, but I prefer to do things myself if it's within my (limited) scope of ability.

So, besides the obvious behind-the-dash connection point, what needs to be removed to route the new cables to their respective endpoints? I know the driver side requires removal of the rear inner fender panel to see that side's endpoint and the passenger side inner fender panel to see the heater control.

Any tricks in routing the cables?

Can I tape up the new to the old and use the old to pull the new thru the same routing path, or do the cables pass thru a grommet that would preclude using that approach?

Obvious, I need help from someone that's attempted this before.

1971 246GT Euro (M-series)