it seems that this model uses a old battery technology and yes, you can remove battery from it
get another battery is another story
https://www.amazon.com/battery-5733Z-4469-laptop-Shopforbattery-compatible/dp/B00I9JWBP6
is it worth to buy? if the battery you have there is dead, then yes, if all you want is more battery time, this one seems to be identical to the 6 cell battery you have now
about the wifi, you need to open it and remove the card, it is the one with two cables one white and the other black, buy another, it should be a mini pci express wifi card, just remove that one by removing the two screws and put the other, put the two screws and then connect again on the same places the black and the white cables
be sure to check it is a mini oci express wifi card, and the one you buy, if this one came with bluetooth, well, you need another with bluetooth too if you use it
the cost of the parts you mentions is around 120 dollars, the laptop itself, is not worth all that, consider instead buying a new laptop with the things you mentiion like a new big battery and a wifi ac adapter