www.autozone.com has free online repair guides for 1995 and earlier Hondas. This
includes the steps for changing the timing belt. Follow the pointers for repair
guides.

One of the biggest obstacles is removing the crankshaft pulley bolt.

See also
http://www.cadvision.com/blanchas/54pontiac/honda.html

http://timingbelt.soben.com/

I removed and re-installed my 91 Civic's timing belt this past summer as part of
a crankshaft seal replacement job. I focused on removing the crankshaft pulley
bolt, spent a couple of weeks researching the matter and trying different
approaches, then actually got it free a week or so before I did the main job.

I ended up making a modified version of a tool another regular here recommended
to hold the crankshaft pulley while I applied the necessary torque (typically
well over 300 ft-lbs.). It worked great.

Others just use an air impact wrench or drive to a local independent mechanic
and have him/her break the bolt free with such a wrench for, say, $10, snug it
back up, and drive home to do the rest of the job.

I suggest sizing up your CP bolt and then asking questions here as needed.

http://www.hondahookup.com/manuals/

If the timing belt broke, then you should consider it likely that there may
be bent valves.  Many Hondas, including your '89 Civic, have an interference
engine.  That is, if the valve is fully open and the piston comes up then
the valve will get bent.  Replacing bent valves requires the head to be
removed.  You can check for bent valves before getting too far into the
timing belt replacement by looking for valves with particularly large
clearances.  Note that bent valves will not seat all of the way therefore
the clearance will be much greater than the 0.008" and 0.010" specs for the
intake and exhaust valves respectively.

Eric