Ask /r/ecommerce: Sourcing and assembly

Hi ecommerce,

I am currently in the midst of developing a product that I hope to sell online or in retail. My product has a custom molded rubber component and a clip (most likely a metal carabiner) attached to it. I'm trying to source these components from alibaba

1. Is this a good idea? What are the gotchas of finding a manufacturer online on alibaba.
2. Who should I be looking for to do the assembly (attaching the clip to the rubber part)? Is this part of packaging or are there factories out there that do assembly if I source the two components separately? Or is this usually a service that would be offered by the people doing the custom molding.

Any tips would be appreciated!