your speedo failure is more than likely due to a broken/failed vehicle speed sensor...
The VSS is on the trans, comes out of the top of the trans towards the back of the engine bay
has a plug and three wires...
there is a 10mm bolt holding a retainer, you should remove the bolt, unplug the sensor and replace it...
you may need to twist it a bit back and forth to get it to come out...
there is a plastic gear at the bottom so be gentle-ish
sometimes they get seized in there...
twisting with pliers should free it...
the IAT is an intake air temp sensor...
no correlation to the speedo unless you seriously fucked up your wiring...
a failed IAT will give you a CEL and affect your col starts, idling and mileage, replace it...
