Hard start, speed sender?

["Salah Khan" <salah.khan@gte.net>]

What does a speed sender do?
I asked the dealer in Tacoma to diagnose the hard start problem I've had on
my V8 (the previous owner had the same problem: approx. 10-second cranks
most mornings,  but sometimes not.  How cold it is outside doesn't change a
thing.)   The dealer retrieved codes indicating my speed sender is
inoperable, and the reference sender "might be" (?) intermittantly inop.
They would charge $650 to replace them (they say labor = 4h) , but cannot
assure me there would be
any improvement in the starting, they would only hope.

I am not familiar with these senders.  Could someone tell me what their
function is?  Will their replacement help the hard cold start? Would anyone
suggest I purchase them elsewhere and replace them myself?  (I have no
special tools, and I'm not a wrench.  But perhaps they just plug in and
out...?)

BTW, they also mentioned that worn crankcase vent hoses could be
involved in the hard start. ($250 to replace them...)
As you might imagine, I would like to avoid having the dealer perform any of
these jobs.

Thanks for any advice on this.
Salah