I replaced a manifold on an Accord just like yours at about 180-200 k miles.
Cracked between cylinders 3 & 4. Best of my recollection, the manifold is
cast iron.  The part is expensive from Honda, I got one from a local yard
for $75 including a working O2 sensor!  Good thing too, because not only was
it $$$, Honda parts had none in their system and didn't know when more would
be available.

I figured I had a leak because it was abnormally hot under the hood in one
spot.  Didn't see it upon first examination, but was evident once the
manifold was off.  Look for carbon traces on the manifold, then look more
closely for the crack.  It will also be hotter in the are of the leak once
the engine is hot.

Don't remember whether I got the manifold gasket from NAPA or
Honda--if it was available at the former that's where I got and it was fine
whichever one it was.  Don't forget to buy new A-pipe seal rings, too.  Good
time to check out your A-pipe as well. Napa has a cheaper alternative than
Honda, that is ok--it may be a tad noiser than Honda's pipe.

No special tools need to remove the manifold.  And, the O2 sensor can be
removed without a special socket once the manifold is out.  The local dealer
may do you a favor and remove the sensor if you bring the manifold to them
with some donuts...  One of the auto parts chains also has tools that you
can borrow for this.

Clean up the manifold there is any rust or pitting.  Must be flat to get a
good seal.

You will have to fiddle with the alternator (?) heat shield to get the
manifold out, but shouldn't have to remove the alternator.  And since while
I'm talking about alternators, if you have a high mileage car, look into
replacing the alternator brushes.  It's a lot cheaper than an alternator and
easy to do.

Check your heat shields while you're under there.  If you ever park on grass
or fields, it would be good to replace them if they are totally shot--they
are not as cheap as we'd like.  If they are partially rusted, but still
sufficient, you can strap them on with heating duct clamps from Home Depot.
Stops the rattles.

Just noticed that you had recently replaced the A-pipe, so ignore my
comments. But you'll still want to buy new steeel o-ring seals.

I had no problem with any of the nuts&bolt even though some were VERY
rusted.  Just heated them with a propane torch and then sprayed liquid
wrench on them AFTER THE TORCH IS OFF--sweated it in just like Cu plumbing
and they eventually broke free with a little repetitive tapping on the
wrench. Watch out for the fumes.

The job can be done in a morning, but leave yourself some extra time if you
have to fight a few bolts.  It's a relatively easy job, no surprises.

Good Luck
PS