not sure about that vendor.. but have bought from these guys.. 1A-Auto and was happy with what i got (window motor).. and now a headlight lens for mamma's van..
but have seen 'em a buck or 2 cheaper.
Was surprised when my local auto parts store had 'em for about the same $$ when I needed a 2nd one for the back door too on the sub!
Good price if they are any good. I paid that much for just one motor from LMC. But, the LMC works fine and is a little faster than the stock GM motor. I'm not a big fan of aftermarket products, they always seem to fall shy of factory parts.
I purchased aftermarket for both doors from napa, both around $45 with a core. Work fine. The only trouble you may have is getting into the door to replace them. There is a site that could walk you through the process, I think it is 73-87.com. The long and short is you have to remove the whole regulator and window from the door to get to it. Not really a fun job. But if necessary take a look at that website.