A 2000 Honda Civic should have a standard AC system. To completely install a new system it will need a condenser, evaporator, compressor, and all the necessary hard-lines. Then the system will need to be routed correctly on the engine and wired into the ECU.
Yeah, but it's not cost-effective.
It can be done for some models. Is there already AC on the '90 civic? If not it will require some effort but it is definitely not impossible.
how tu install CD player in Honda civic 99
You can change a Honda Civic HX transmission to a manual transmission. It is not an easy job to do.
The 2011 Honda Civic has a 5-speed manual.
The 2007 Honda Civic has a 5-speed manual.
The 2004 Honda Civic has a 5-speed manual.
The 2009 Honda Civic has a 5-speed manual.
The 2008 Honda Civic has a 5-speed manual.
The 2003 Honda Civic has a 5-speed manual.
The 2013 Honda Civic has a 5-speed manual.
The 2010 Honda Civic has a 5-speed manual.