First, ask the mechanic exactly what he's going to install.
In particular, you want to know if you're getting

-- a new distributor housing
-- a new coil
-- a new igniter

I agree that $300 is a good approximation IF only the
igniter and coil were being changed. The guy should be
willing to take into account the diagnosis charge, as well.
So you'd pay like $240 more for JUST a new igniter and coil,
tops. Or that's what seems reasonable to me, as far as
charges go. That's not bad.

HOWEVER, and it's a big one, it is not IMO completely out of
line for a shop to find a bad igniter but also notice, on
this really, pretty old Honda, that the distributor housing
O-ring is old, there's some indications the housing bearing
is going bad, the wire harness is looking beat, etc. Plus,
often the rotor set screw female side starts getting strip.
On a car this age, if the shop only replaces the igniter, a
comeback is a pretty good possibility. For example, a bad
igniter can have detrimental effects on the coil (or it's
the other way around). So a whole new housing, plus new
igniter and coil are, in my estimation, a good idea for a
car this age. Your car will run like a champ with it,
assuming ignition wires, plugs, cap and rotor are in good
repair.

I thought I got taken for a ride in spring 2003 back when a
shop installed a new housing (because of rotor set screw
problems). Cost me $472 JUST for a new housing, cap, and
rotor. They reused the old coil and old igniter. I was back
a week later with the real problem: A failed coil. I was
miffed at the time.

In hindsight, knowing the distributor wire harness was
pretty beat, and I think oil was leaking down the
distributor yada shaft, and the bearing might have had not
much more life, I think it was a good investment. It wasn't
handled well, but then they don't have time to explain all
these details to consumers, especially since most consumers
don't have a clue about electro-mechanical yada anything.

They were pricey, as well. Point being, that, given the
price you quote, your mechanic may be being more reasonable.

My 91 Civic had 138k miles on it in spring 2003. It's been
almost three years, and the car has not seen a shop since,
though I'm watching it myself closely these days. I actually
installed--myself--a new igniter back in 2003, 'cause the
guys at the shop were saying I should, given the bad coil. I
just didn't want them doing it. :-)

Take a look at www.slhonda.com 's parts site to see the
exploded view of the distributor and what are probably the
best prices for genuine Honda parts that you can get. Maybe
consider printing out the drawing and labeling the parts,
then taking it to the mechanic and having him tell you what
he's going to replace.

Make sure he's using genuine honda (= OEM) parts. Non-OEM
distributors distributors tend to have short lives.

Updates are welcome.

No, not yet. Let us know what he's going to replace.

One other thing: I just checked the two online OEM Honda
parts sites that I use a lot, and both quote a much lower
price for your 92 Civic's distributor compared to a 91
Civic's distributor.

For a 92 Civic LX, www.slhonda.com wants only $271 + maybe
$10 shipping for I'm pretty sure the distributor housing,
coil, and igniter. All OEM. The housing by itself goes for
$97 for a 92 Civic.

A 91 Civic's housing is about $280(!) at the same site, as
well as the other site I use.

I don't know why the 91 and 92 have such big price
differences, but use the prices at the site above to help
your decision-making. That $500+ charge now certainly looks
like a ripoff, any way it's cut.