Here's a pic of the OBD II connector (in the yellow box):
Here's a couple of links to OBD II forums. The 96 Metro uses the ISO 9141 protocol. You can search through them for info on scan tools. The Metro uses pin 9 for the air bag system which is different than what a lot of the tools use for diagnostics. Just something to keep in mind.
http://www.mp3car.com/vbulletin/engi...agnostics-etc/
Scan tools are cheap too. Here's one but there are others. Just search the above forum. Edited the bad links.
http://www.obdpros.com/
As for the 95 to 96 engine swap, you will run into problems if you need to get it inspected, or at least I think you would. Up here, all 96 and later models require hookup to OBD II scanners for state inspections, so unless you can do as Mike_Van suggests, your car may not be inspectable if you don't have all the sensors.
Hope this helps