I don't really know whether to give you the best answer I can or to point out that you really should make your intro post a true introduction, and then post your question in another thread. That would make the staff and moderators happiest.
Why don't I try to split the difference:
Glad you joined up! Tell us about yourself.
Now as far as that motor goes....That appears to be a somewhat upgraded version of the basic 2-stroke, in-frame motor that is known around here as a "happy time". Many of us believe that the happy time is just the right motor for beginners. The reason is that you can get them cheap. You're not putting a lot of money at risk. It will ride you around fairly reliably (though beware; there are quality control issues. I'll address that a few lines down.) long enough that when you finally do have to give up on that first engine you will know whether you want to replace it with the same thing or move on to something that's a bit more expensive, but higher quality.
If you are new to motor assisted bicycles, then I would definitely recommend a happy time engine. I can't quite judge whether that particular one is upgraded enough over the basic happy time to justify the higher price. Maybe other members will come along who have a better notion than I do.
These engines seem to be slapped together in some overseas factory with very little quality control. The vendors are really not responsible for this, it's just the way things are. But this makes it important that you buy from someone who is trustworthy. Don't buy from someone on e-bay simply because that's the rock-bottom price. You can just about count on zero product support.
Vendors with a reputation to protect will surely be more concerned with you receiving a product that at least works. Be careful that you don't void the warranty by, say, breaking the head or something like that. Avoiding that, you should find your vendor to be reasonable.
I've never bought from bicycle-engines.com. But I don't recall hearing any bad publicity.
If I were making a purchase right now I'd feel confident placing an order with them, as well as a handfull of others.
Best of luck to you. We hope you build yourself a bike successfully, join us and have fun.