water pump related questions

[id <ionicdesign@xxxx>]

i plan on doing my water pump and the hoses under the manifold but i have some questions
about some of the parts involved.

there is a coolant Y pipe 102147 under the intake manifold that has these parts in it
102478 lambda sensor and 102405 therm vac switch. since i will be in this area how do i
know if these two parts are bad (102478 and 102405)? what do they do? should i replace
them?

also the thermotime switch 102125 what does it do? should i also replace this too?

thank you
mark
VIN# 6683