I'm not familiar with an Ektar, but I dissassemble my lenses all the time.
All you need is a simple spanner wrench.  I have yet to meet a lens where
"tricky spacing" was required.  Everything just fits together.

I did, on my most recent dissassembly, botch the reassembly by not
properly seating an element.  I noticed, and then corrected the problem.

  The 90mm Enarging Ektar is a new one to me. I am familiar
with a 100mm E.Ektar. If its this lens its a four element
air spaced type. The outside elements are held in place by
retaining rings.
  The cells unscrew from the barrel. The rear one has a
flat surface at the back of the barrel. It can be gripped by
a stick rubber surface like a latex glove layed flat or a
rubber jar opener (I can't find these any more). The front
cell is a little more complicated. Its front looks like a
retaining ring and is the part with the Kodak label on it.
This can be gripped with a friction wrench made of a tube
the right diameter with sticky rubber on the end.
  The outside elements of each cell are held in place by
more retaining rings. These can be seen inside the outside
facing openings of each cell, just around the glass. These
are also removed by using a friction wrench. You will have
to make the wrenches to fit the rings so that they do not
touch the glass. The tubes can be metal or whatever will
fit. One can make the gripping surface from liquid latex or
from O rings cemented to the tube. I've not had much luck
with O rings.
  If this is some other version of the Enlarging Ektar
write back. AFAIK they were made in focal lengths of 50mm,
75mm, and 100mm, but there may have been others.