Can locksmiths be trusted?

If it feels they are rushing you and avoiding telling too much, then it may be a sign they can't be trusted. Another way to get a better feel for their skills is to check their experience. While never a guarantee, locksmiths with 10+ years' experience are usually the most skilled so can probably be trusted.

Why is it called locksmith?

When you need a new copy of your apartment key, you can also visit a locksmith. The word comes from lock and smith, from the Old English smið, "one who works with metal."