DumbAss knows what he's talking about, heed his words. (Oh and hi there DumbAss, I recently realized you are a local who I have met before at a repair party!)
Here are my two cents as someone who has grown in to doing a little of this kind of repair.
Replacing .156 connectors is hard to screw up if you take your time. Any connector with obvious damage should be replaced and I think this is a good skill for people to learn, if they intend to be a long term owner of these games. If you do make a bad crimp, you can re-do it... it is unlikely to cause a catastrophic failure as long as you keep all the wires in the right places! The parts and tools are inexpensive, too.
Replacing headers is much more involved. With a little prior experience in soldering I do think it is an attainable next step for almost anyone. However, no one should attempt it if they are not emotionally and financially prepared to goof it up and pay for help. Also, I would not attempt it if you can't budget for the right tools... a good soldering station and critically, a good desoldering tool. You should also have a DMM with a continuity function. That adds up.
A lot of the skill lies in diagnosing problems and knowing what to replace. Like DumbAss said, "if it ain't broke don't fix it." But there can be exceptions to that rule too, which grow in number as your skill grows. Everyone has to find their own way.
(When I fixed my first non-booting game with a header and connector replacement, it was worth every dime I spent on tools, and every minute spent on research. YMMV!)