Just do it yourself.
It doesn't take a genius. Check the beginner lessons here... I'm not sure if they're still available without a membership, but it'll walk you right through it.
If not, just use Google and look up 'how to change guitar strings'. You'll probably find hundreds of lessons.
Considering that you'll probably changed your guitar strings a few hundred times in the next 10 years, it's well worth learning it yourself.
While you're at it, study up on setting the intonation as well.