The biggest worry is whether the battery will fit or not – I replaced my Teclast x98 Air 3G’s battery awhile ago and ran into problems with bulging and screen/touch digitizer contact (the dreaded bubbles). You will also run into issues with less-than-reliable mAh claims by various sellers – keep a very close eye on reviews of sellers and especially the negative reviews, as you know stuff from China is very hard to return/replace.
If you do successfully replace it and you notice the capacity is less than you would expect, give it a few cycles before judging – I had the same issue with my x98 Air 3G and figured the battery was fraudulent, but found that the capacity improved after 6 or 7 cycles.