I once read somewhere that good writers are normally not aware that they're good, so I guess if I set out to show you how good I am, it would be a sign that I'm actually not all that.
So instead I'll ask you to let me write a sample description for one or two of your products, and that way you'll be able to judge for yourselves.
As for the time I'd take to finish the project, I've just guessed at what I'd call a reasonable time, but I can't really say seeing as you haven't given a clear picture of what the workload is. Having said that, when one is inspired to write, the limiting factor is your typing speed! And mine's not too shabby.
Let me know.