Welcome on man!
As for the harness, it's not worth the hassle at all! It's more cost effective to sell a great running 1.8 to some kid and buy a turbo or 2.0 N/T car. If this is the desired route the whole harness up to the computer will have to be replaced, yes nothing about them is the same (primarily becuase of the ignition system variations). However if it's the turbo route your wanting to take it's easier to install but more difficult to find parts. I have been working on gathering everything for almost a year now and just about ready to instal the whole setup. The 1.8's have advantages and disadvantages, you just have to think about it in a same but totally different way. Mischif, Sandcobra and I have some very "potent" 4G37's.
89Gold, check out dsm1eights.org sometime. Lots of great info over there as well for high build 1.8s.