Find and replace using 2 text files as arrays.

Here's the nonfunctional code I have so far

 
#!/bin/bash
searchFor=(`cat filea.txt` )
replaceWith=(`cat fileb.txt`)
myMax=${#searchFor[@]}
myCounter=1
while [ $myMax != $myCounter ];
do sed -i 's/${$searchFor[$myCounter]}/${$replaceWith[$myCounter]}/g'
done

The goal is to use each line in filea.txt as a search term, and each line in fileb.txt as a replacement term. Then I would like to point the script toward filec.txt and replace all of the terms.

Try this:

myifs="|"
paste -d $myifs filea.txt fileb.txt | while IFS=$myifs read a b
do
        sed -i "s/$a/$b/g" filec.txt
done

one problem: there are spaces in "thing 1" and "replacement 1"