I've got a BA xr6 and I had a missfire a few weeks ago and it's making my car cough and splutter,
I'm gonna buy some off eBay and change them myself

1- is it hard? And how would I go about doing it? What do I do

2- which brand is more reliable

No its not hard to change yourself especially on NA. Take the black cover of on the rocker cover and carefully pluck them out unplug and replace.

Which brand ? Me personally - Genuine or nothing.

Id also put a fresh set of good quality plugs in as well to compliment the new coils.

hi mate, i just changed mine recently.

i got them of a Australian ebay seller which also happen to be a ford enthusiast.

here is the link

http://www.ebay.com.au/itm/Ford-Falcon- ... 2ecfec3f18

the ba bf is tempremental when it comes to replacing parts or when parts dont work as they should.

i would go for a reputable brand such as vdo, or genuine ford, i went for vdo because they were a little cheaper, but in the past vdo have made good parts that alot of cars have used from factory, chances are ford get vdo or bosch to make these bits anyway, they are just stamped ford instead of bosch or vdo so they can sell them as the "factory part", but the direct manufacturer wont ask for an arm or a leg in exhange for the same parts

make sure you do the spark plugs at the same time because chances are they are rooted or close to it.