Unfortunately you have been scammed.  It takes an hour at most to do a rear
wheel cylinder.  As far as the other two items, you, yourself could replace
them in less than 30 mins (I could do both of these items in less than 10
mins).  The temp sender and Idle stab unit are both plug in units.  The idle
stab is pricey (around $300 if I remember right) but the temp sender is only
around $10 and both are pretty much plug and play.  The temp sender is the
only slightly less straightforward thing here.  You have to pull a clip, pop
out the old one and pop in the new one quickly so as not to lose coolant, but
then you just plug it in and it is good to go.

The idle stabilizer probably was bad (they go bad alot and people just live
with them) but he should have called you before slapping on an expensive part
like that and given you an estimate on time as well.  Hope this helps.

Thanks,
Ken Wilford
Van-Again
John 3:16
http://www.vanagain.com
Office: (856)-765-1583
Fax: (856)-327-2242