Is this a great pc?

Great for what? For gaming at 1080p? then No.

The CPU is getting old and comparatively weak to what is on the market today and the GPU is now 2 generation behind the current gen and was low end when it was new. It also looks like a no name low quality PSU which would need replacing before ever considering a new GPU
 


what is your budget?
there are a lote of videos on youtube showing you how to build, don't be worried.
and if you are going to build one, the components itself have warranty. i would suggest you to buy from local store
the components because they will handle everything themselfs if something won't work...
 
I would not buy/build with a FX processor today. The cores are simply too slow.

Do not worry about warranty.
The warranty of a prebuilt is only as good as the seller.

On the other hand, the warranty from the parts manufacturer will often be sufficiently long.
Intel processors are 3 years, and many graphics cards are 3 years direct from the manufacturer.
Ram is typically lifetime and a ssd will be 3-5 years.