echo area key binding

After a quick scan of the manuals, I haven't sussed out how to do the 
following - suggestions appreciated:

In the echo area of the LW editor, I want to swap the functionality of 
space-bar and tab.  When I do ^X^F (WFind File) I want space-bar to perform 
"Complete Input" (like gnu emacs), i.e. when I hit ^X^F I get a Find File 
dialog - I want to type the first few characters of the file name, then hit 
space-bar to complete the file name.  The default binding of Space Bar is 
"Complete Field", which seems to do nothing useful in the middle of ^X^F.

[After over a year of using the LWW editor, I still instinctively hit 
space-bar instead of TAB in the middle of ^X^F.  Maybe it's time to admit 
that I just can't learn to hit TAB :-].

When I do succeed in changing the functionality of space bar in the echo 
area, am I going to suffer unwanted consequences with other echo area 
functions?

[The other Gnu Emacs feature that I sorely miss is split-window-vertically 
(two views in the -same- window).  As far as I can tell, this just can't be 
done with the LW editor - correct?]

Thanks
pt