A Few Basic Circuit Board, Solder Joint Questions

[shertex]

I have nice, GDL-rebuilt cruise on one of my cars....money well spent. Since I'm finding it hard to justify the cost of a proper rebuild on my second car, I thought I would deal with the solder joints on the amp myself and hope for the best. While I took an electronics course a long time ago, the only time I ever really used a soldering iron, I could use some help with some of the basics.

1. Is my goal to remove and then reapply the solder at each joint? Or is the goal to heat each joint to restore conductivity?

2. Assuming that the goal is to heat the joint, can someone quantify for me exactly what I need to do? I assume I need to touch each joint with x-watt iron for y-seconds and to make sure that the solder doesn't run. Do I heat the joint until it's shiny? molten? Some other criterion?

3. Is my 35-watt iron adequate or do I need something else?

I've been reading some related threads....my apologies if I haven't noticed answers to these particular questions.