Nissan Maxima Brakes Question - Year 2001

Have 40k miles and noticed brake pads a bit thin. Also a little squeak
out of the right rear brake. There are Disks all the way around.

I usually would go to Nissan as I had a bad experience one time with
some pads that deteriorated and warped my rotors worse than they were.

I noticed the rotors were somewhat scored so I had all rotors turned. I
also had this done since when I stopped, the front of the car would
shimmy a bit which got worse over time (all wheels are aligned, new
tires, etc...).

They removed the stock (came with car) brake pads and used Ceramix
Brand (#7421). I asked if these were compatible with the Nissan Maxima
and they said yes.

1***Do you think these pads are okay? Or should I have Nissan pads
which perhaps may be made out of another material?

2***Unfortunately Nissan told me (I did not take car to them for this
job) that they have an entire new caliper assembly I would need to
shell out another $150 for since they (Nissan) found out it was
somewhat more powerful than the stock one Nissan supplies. I asked why
this was not considered a recall and they simply said it was not.

So basically would like some input on #1 above with respect to brake
pad type and if I am okay and comment son #2 from Nissan owners.

Thanks
Patty