Go to Honda's web site.
It depends if it's manual or automatic and if you have someone else do it or you do it yourself. You can get a used transmission from Japan with under 60K miles for a 5 speed (which actually run higher priced than auto), which is under $600 shipped if you look on eBay. You'll need something like 2 quarts of manual transmission fluid. I used Pennzoil Syncromesh, which is $9 a quart. It's not recommended by Honda, but it works very well. Then it will take 2 to 5 hours to swap the transmission out. You're looking at under $700 if you do it yourself, assuming you use used parts. If you want estimates for what a shop will charge, call them.
The heater core is under the middle of the dash, mounted to the inside of the firewall.
It is a very difficult repair, as it is extremely hard to gain access to it.
This is true for the majority of vehicles, only a few models have easy access to the heater core.
In this particular vehicle (92-95 Honda Civic) the front seats, center console and entire dash must be removed along with the knee bolster framing, you can however disconnect the steering column and let it lay in the floor.
The core is accessed via a small panel on the bottom of the air mixing box.
Be careful and do not let weight hang on the wiring harnesses when removing the dash, also when re-installing the dash be sure to not pinch any wires.
Because of the difficulty of the job be sure to use a brand new high quality brass heater core replacement, don't use crap, it is not worth a few dollars in price to have to do it all over again.
Be very careful of the airbags, be sure to disable them properly.
To do so, disconnect BOTH battery cables, let car sit for 5 minutes without any power.
Open the access door on the bottom of the steering wheel and use the red shorting plug on the airbag cord, do the same on the passenger side after removing the glove-box.
be sure to keep your head out of line with the airbags while disabling them.
Handle the airbag modules carefully even while they are disabled.
I just completed this job yesterday, it took me 5 days worth of spare time and being careful. Take your time and you will be OK, also get a good helper.
Labeled baggies for screws and bolts as well as digital cam pics of the process will help tremendously.
underneath the steering wheel. it should be to the left of the fuses and whatnot.