I do not think you need to go out and buy a different machine quite yet nor do I think you need to have it serviced - the cost of servicing is likely not worth what you even paid for the machine upfront.
Agree with NJ Quilter - please double check the manual and make sure you've threaded it correctly? Overstock.com had over 40 reviews on this machine and a couple people mentioned the threading was kind of tricky? I don't know this particular machine so I couldn't say, but I know threading my featherweight is still tricky for me!
In regards to what kind of shank, here is a link that explains it pretty well:
https://madamsew.com/blogs/sewing-bl...s-presser-feet
As to how big a throat you have, you simply get out your ruler and measure the distance from the needle to the base of the machine directly to the right. Basically, how wide the "hole" of the machine is.
I do also suspect that your top tension is too tight, so keep making small adjustments and seeing how the stitches look as you sew a new seam. Here's a brief article on tension:
https://www.thesprucecrafts.com/easi...ension-2821432