First probe and tool height choices

Hi!

I'm noob, I have not made any probe or tool height's yet. I want to find my workpiece coordinates and workpiece top height. So what I must do? On Mach4 there are these choices:

On Tool Information there is Touch button, from there I can choose:
Find workpiece Corners. Plug in my probe, insert probe tip diameter. Press desired function button(Left corner)
Find Z(material top). Plug in my tool height sensor, insert Touch Plate height. Press desired function button(Find Z)

On Probing tab:
Corners, Measure corners
Single Surface, Measure Z... So this is for only for probe, not for tool height sensor?

On Offsets tab:
Coordinates, say G54
Edge Finding. Insert Edge Finder Diameter(probe tip?), Set X, set Y
Z Offset and Tool Offset, both have insert Gauge Block Height? What to choose?


What is the right and precise way to measure Touch Plate height?
Do I need fill the Tool Offsets?
Tool changing. Can I jog machine to some place where I want to change the tool, place where I measure tool height, and what to press after that to go back to position?

Setup:
Homebuilt CNC, Mach4, ESS, with limits and home, one probe/tool height signal input, 2.2kw spindle, ER20 collet.