heres a website that has a rebuild kit for a 1990 ka24e. http://www.rpmmachine.com/engine-rebuild-kits-nissan-4-cylinder.shtml
for $353.21 you cant go wrong.
and your best bet is to do it yourself. to get someone to do it they charge you up the ass. and if you dont know how to do it ask someone you know.
Major Engine Kit: contains complete gasket set, set of pistons and rings, main bearings, rod bearings, thrust washers, timing belt, balance shaft bearings (if applicable), and a set of expansion plugs (does not contain camshaft, timing kit or oil pump). Pistons & Rings: Std., .020, .040. Bearings: Std., 10, 20, 30.
I know of a SON member who picked up a 95’ KA24DE engine, 5 spd tranny, and ecu with only 44,000km on it for only $800 bucks - with that being said shop around, there are always deals to be found out there - everyone gets lucky