Seeking basic wiring explanation of speedo connector block

[helloindustries]

So far; This thread has been quite a learning experience for me. Very handy, too. It's appreciated.

I admit i'm having a little trouble distilling posts in to a list of things i'll need to do to when installing the Koso speedo.
Far as i can see, beyond the wiring diagram i've posted...

• I can reasonably ignore the over temp warning light.
  
• I may need to run a wire from the existing speedo to the Igniter box (whatever that is) and a black/blue wire (which i don't see anywhere) to the speedo to maintain a required circuit. But i may not need it at all.
  
• Something about a resistor of some type from existing speedo to Koso (so; Don't use the included magnetic sensor for the Koso?)
  
• Something to do with a pull-up resistor (whatever that is)
  

I don't mind admitting that i don't understand exactly what i need to do. This isn't my area of expertise. Graphic design is. I tinker at best, but i can manage the physical installation and such (clamp here, add connectors to wires there, install specific component between A and B etc...).
What i'd need before attempting this is very clear descriptions of what all these extra bits are. For example: What is a 4700 resistor?