Brake Caliper replacement

1987 Cadillac Sedan Deville, 106,000 miles.
In replacing brake pads my friend ripped the piston gasket on the left front brake caliper. We bought two calipers, left and right front. However he can't for some reason get the new left front caliper re-installed. He for some reason can't get it lined up, I called the auto parts and they assured me it is the correct caliper. I need to know if there is a special procedure for lining up the caliper so the bolts will go back in. As well does the brake line need to be connected before trying to put the new caliper on? Should you do the top bolt first? Bottom bolt? Is there a certain way to re-install the caliper? He has tried to no avail, and I nor he can understand why he cannot get the caliper back in place. He says he has done this before and it should'nt be this difficult. Could the new caliper be the wrong one?