Programming :: BASH: Read + Define + Modify A Numeric Value From/to A File?

I want my bash file to read from "input.dat" the two values emin emax. My input file looks like that:

#cat input.dat
!Energies
emin 10.00 !minimum energy
emax 30.00 !maximum energy

Now this seems to be not so hard with the command awk

#!/bin/bash
awk '{FS=" "}/emin/{print $2}' input.dat
awk '{FS=" "}/emax/{print $2}' input.dat

[code]....

So far so good. Now, I want to define two variables (e.g. e1,e2) in the bash file, so that their values would correspond to 00.00 and 30.00, as read from the input file. This one I have not found yet, thus asking for your advice. At the end, writing echo $e1 $e2, I should get 10.00 30.00 This is even harder to me: I want to replace the values emin,emax in a new file "modify.dat" which looks like that:

...
c---- energy interval
emin = 1.00
emax = 2.00
...

with the values e1 and e2 I have in my bash file. In other words, I want to call "modify.dat", find these two lines and replace the numeric values with the e1 and e2. At the end, my file should be like:

...
c---- energy interval
emin = 10.00
emax = 30.00
...