Omega at MOE send it away and it takes about 10 days
They are ridiculously overpriced and quoted me AED1200 in the end i took it home and had it done there for GBP45 they also sealed the back as many of the cheaper places here don't do that
At Omega in Mall of the Emirates (and probably other places).
Very slow though, so doesn't really answer your question.
Sure someone will have an idea of somewhere quicker but if wouldn't be an official Omega service centre.