As other have said, it is not an easy swap as the engine is rare and only came installed on Sidekick Sports for a few years.
The 5-speed transmission is the same one as found in the 1.6 Sidekicks and Tracker with two important diferences:
1. Fifth gear is not the same. In order to get the best performance at high speeds (highway driving), you really need a tranmission geared for the 1.8 engine
2. The 1.8 engine does not have the same mounting setup as the 1.6 engine! The 1.8 uses a bellhousing that both mates the transmission to the 1.8 engine AND has a hydraulic clutch system.
(end personal experience)
What does this mean? You need to find a 1.8 engine and transmision - preferably a 2WD engine/transmission combo to make it easier to fit it all in with your Samurai transfer case. Good luck doing that...
Yep, it is better to find a good 1.6 engine and use a commonly-available adapter kit to connect it up to the Samurai 5-speed.
Also, You can get the engine with the wiring harness/ECM OR get an aftermarket carburetor kit and dump the electrics altogether if the local authorities allow it. Right now, the MYSide (ZOR Zuks Off Road
Tell them Ack sent you - they'll probsbly say "Who??") is the most popular system in use. Great product and support. (This is an unpaid endorsement - the best kind.)
I hope that this helps!