I just replaced the front pads and the brake fluid on my 2001 Civic! It
took 3 hours, making sure I do all things right, but now the car runs
fine, it doesn't squeak, no weird sound, the brake pedal is firm (not
mushy). The only "problem" was that the new pads barely fit in the
calipers, there was very little clearance.

Also, the Honda OEM pad set came with 6 shims, but when I opened the
calipers I found shim only on the back of the outer pads, no shim on
the inner pads. So I just used shims on the outer pads as well. I have
some shims letr, I guess the same "kit" is used in other cars (Acords,
Acuras?) and maybe the put all the shims there to make it an universal
kit.

why are the shims needed at all?

The kit came with some brape pads greas, which I applied to the back of
the pads and the shims.

All in all, I saved 180 bucks. The mechanic wasted 180 for brakes and
40 for the fluis, and I paid 40 for all the parts (pads and fluid). So
not a bad deal after all.