Welcome back from the real world. Also, thank you for your service.
Looking forward to seeing this come to fruition, the smog rules here in SoCal make doing those modifications a pipe-dream.
If you do a wideband it would be best to have it in the J pipe and the secondary O2 in the mid pipe. The MSP has an O2 extension harness to extend the wiring since the O2 is on the midpipe instead of the J pipe like the NA cars.
Can you post a photo of the pipes you have? If they are for an SMIC they should fit fine. The ebay piping sets are universal, you have to cut them to fit so you can make them work no matter what.
That core is way bigger than you will need, you would have to remove the crash bar to fit it. You can use a universal piping kit for that FMIC or set it up for an SMIC.
That's how both of my FMIC kits are, I had to put a slim fan on the passenger side. On one car I was able to make the stock driver side fan fit, and on the other I used two slim fans.
The ebay slim fans work, but are not very good to be honest.
I was able to make my piping fit without modifying the bumper at all, I recommend going through just to the side of the radiator on the passenger side, and up through the hole on the driver side.
You can make it fit, but it does take some work.