I changed the front brake pads on my '90 740 wagon (Girling calipers) recently. The left front caliper was very tough to retract back far enough to get the caliper and new pads to slip back over the disc. I was carefully using a woodoworking clamp and a block of hardwood to compress the caliper, but it was impossible to budge (the right side was a piece of cake). FWIW, I removed the master cylinder reservior cap prior to the work

Getting desperate, I retracted the large rubber boot from the sliding part of the caliper enough to see that there was rust and pitting on the caliper piston. A bit of light sanding (yes, not the best thing to do, I'm sure) and a small amount of brake grease on the piston made it possible to retract it enough to finish the job and get rolling again.

Now, however, the brakes are mushy as heck, and at times I think the ABS is even kicking in a little when I'm nearing a full stop.

I'm assuming two things:

A: that there is air in the system (though I'm not quite sure why),

and

B: that I need to replace the front calipers.

How tough is it to change the calipers? I see from the FAQs that a few doses of PB Blaster a few days prior to the job is worth while.

How hard is it to bleed the brakes? Will I be bleeding only the fronts, or do I need to do all four?

Finally, I found rebuilt calipers online from alloemparts.com for $65.00 each, while most places want nearly double that. Does this sound to good to be true?

Thanks for your comments.