300e ac evaporator core is toast

Hello,

Just found out why the ac in my '89 300e won't hold a charge--mechanic says
the evaporator core has failed and he needs $1,600 bucks to install a new
one. I've never installed one myself but it looks like I'm going to now
because I've got more time than I do money.

Several mechanics have told me that the whole dash has to come out to get it
out and I don't doubt it. I'm not looking for a step by step by any means,
just any tips for avoiding the big "gotchas" and things like..

how long should it take me (of average or better skill) to do the job
if I need any special tools
how I can check for leaks after it's installed but before I re-install
the dash
if there are any other parts that I should also replace while the dash
is out
and who's a good source for the core

Also, I can hear one of the flaps in the ac ducting making a thumping or
popping noise about every second or so (when the ac's on of course) and
there is little or no air coming out of the center vent. Is that because
one of the actuator pots has failed or is it something else? Can I tell if
the pot has failed by inspecting it visually or do I need to take a vacuum
on it to find out?

As for the cost of the part(s), thebenzbin wants $282 with the "valve",
$186 apparently without the valve, and ACKits wants $145 also without the
valve. Is one of these going to be better quality than the other and should
I replace the valve also.

My last question has to do with the cost I was quoted by my mechanic. Both
of the evaporator cores on thebenzbin have a suggested retail price of $960.
I know for a fact that my mechanic has charged me or quoted me the exact
same suggested retail prices shown on this website for several other high
dollar parts and I'm wondering if $700 or so of that $1,600 bill is a markup
for the difference between the two costs of the part? I'm not grudging my
mechanic the ability to make a decent living but is it customary and does it
seem right to charge $70 per hour to do the work AND markup a $200 or $300
part 300 to 400 percent?

Thanks in advance for your guidance and comments.

Mike

Yep, that $700 markup is true. But before you change out the evaporator on
your car... check for leak at the expansion valve... it is very easily
missed and declared that the evaporator is leaking.

Just follow the AC line going toward the interior of the car... they
probably already did the dye injection... it is kinda just below your wiper
location way deep inside... if you can flash some light in there... if you
see alot of light green colors, then you know it is leaking like crazy
there. If you get the UV lightpen, it will glow purple/green.