New faulty lens didn't focus properly at wedding shoot....

Taking a few trial shots is, to be honest, not the way any Pro would work.  Taking on weddings requires complete confidence in the equipment and backup equipment.  In addition, there is a requirement to have full insurance cover, so I assume from your general comments that you are an amateur who thought it would be a nice little earner to do weddings.

I accept that it is disappointing to have such a fault but to take on a wedding without real knowledge of equipment (or any Pro work for that matter) just is not acceptable.  End result could have been (may be still?) disastrous as these days, people are well into the (unfortunate) American process of suing when anything goes wrong.  Let's hope you don't fall into that trap and you will at least have learned from your experience.

Professional Photographers know only too well that years of success and respect can be wiped out from just one unsatisfactory project - basis of the expression:

"You're only as good as your last job"

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Zone8: Although I am a handsome genius, when I stand in front of a mirror, I vaguely recognise the ugly idjit standing on the other side!
LINK: For B+W with Epson 1400 (and other models) using black ink only PLUS other useful tips:
http://www.photosnowdonia.co.uk/ZPS/epson1400-B&W.htm
Cleaning DSLR Sensors, including Kodak DSLR Factory Cleaning method:
http://www.photosnowdonia.co.uk/ZPS/KodakDCS-sensorcleaning.htm
Solving back/front focus problems on Sigma and most other DSLRs
http://forums.dpreview.com/forums/read.asp?forum=1027&message=35565277
PDF format list of lenses you can print or download - covers Italian Flag YES/NO for DCS 14n but applies to others. http://www.photosnowdonia.co.uk/ZPS/ItiFlagLensList.pdf