HELP!! Pre Qualified vs. Pre Approved

[Karen Margrave]

Trying to help a residential buyer. Most of the listings now want pre approval over pre qualification for obvious reasons, and prices are going up daily here. However; on pre approval, the buyer wants to know if she goes to two different lenders how would it affect credit score? (one lender doesn't do FHA loans, the other does - but from discussions it seems they won't loan as high as the FHA lender) Also, how long is pre approval good for ? She's concerned with credit score getting lowered, etc. Any insight, and advice will help. I usually do commercial land, development, etc. and need a little refresher on residential financing.
@Will Barnard, @Bill Gulley, @J Scott anyone? THANKS!!