Hello hupo224,
This is good timming, I just now finished putting a hitch from a '98 on my '97. The nutstrip has to be installed on the drivers side (US Version/Right Hand Drive). I would suggest you chase the nut strip, nuts with a tap. You will need a 12mmx1.75 tap, get the die as well, incase you bugger the bolt. The bolt you need is a M12x1.75x45mm.
You need to remove your bumper, I used a 10mm socket and wrench to remove the plastic bumper material from the metal section of the bumper. If you remove just the metal bumper section, and not the bumper supports. You can get a shallow socket 15mm on a 3/8's ratchet in there, it is easier if you have a flex head ratchet.
I bring this up because once you install the hitch, you will be even harder pressed to remount the bumper, if you removed the bumper, and supports. Theres a 15mm flanged nut on the top inside of the metal bumper section, and a 15mm bolt under the bumper. Just pull back the plastic end caps, and remove the metal bumper section.
The factory strips are riveted in, they do not hold well. I drilled them out and installed self tapping M8x1.25x25mm bolts, they have a 10mm head pattern. They will tap into the strip, trick is to install a prybar or something to hold the strip down, while the self tapping bolt is being installed. Once you tap in the nut strips, chase the threads of the nutstrip, you should be good to go. I hope this helps you out. Scott.