You have to remove the front bolts on the seat rail to fit the bracket underneath (there are plastic covers that need to be removed to get at the bolts – they are replaced after – https://www.youtube.com/watch?v=YmGAspMqBRk should give an idea of how to remove the covers) — once the bracket is fitted the bolts (Torx e12) are put back in through the bracket and the rail and bolted down (36 ft/lbs is the torque requirement if I recall). The seat stays in place during the process.
Yes – the bracket works with manual seats (mine are manual) — the lever to unlock and slide the seat back and forth still works as designed.
The bracket still needs an extinguisher with a metal clip down bracket. I bought a “Garrison” 2.5 lb extinguisher from CTC (http://www.canadiantire.ca/en/pdp/heavy-duty-1a10bc-fire-extinguisher-2-5-lb-0460078p.html#srp). It has the appropriate metal connection.