Ease of upgrade?

So i ordered a TwoUp that should be here by the 19th of December.I know i know, its not the best machine but hey, it can hold me over and i can learn a few things from it until my overlord comes in march. Now my question is, How easy is it to improve build area? For the Z axis of the Twoup, can i buy 400mm linear shafts and a 400mm lead screw to increase the Z axis build area to 350mm? Is it as simple as just switching those three things out? I mean extra supports yeah but in general. Is the software the only thing that determines how far those motors will push that gantry up?

I don't know that machine specifically but in general there are variables in the firmware that tell the machine where it's maximum extents are. The second thing that controls it is the home switch and/or any other limit switches that may be on that axis. Third is the slicer software IF it takes your specific machine into account when creating program files.