Help with Squirrel erradication in attic

Not sure this falls under home maintenance.... but not sure WHERE to ask for help on DG.....

My son has a home that we are remodeling that was bought out of foreclosure in late July. We live 2 hrs away and can only work on weekends so the remodel is taking a while. We have made a lot of progress, but still several things left to do. One of which is to repair the screen that is on the eaves of the house. We haven't gotten to that yet because we have been dealing with much more serious issues on the inside of the house - and trying to get the place much more livable..... BUT, we think he has an infestation of squirrels in the attic. We have tried repeatedly to "see" them but we can't. He has a split level house with a low slope and about the closest we can even get to the outside wall in the attic is about 10 - 12 ft. THey are keeping him awake at night, and he thinks they are chewing on things - of course, if it is wiring, that could be a major problem..

Just thought someone here on DG might have some suggestions as to how to erradicate them. We considered a pellet gun, but we dont own one and since we can't actually lay eyes on them, we didn't feel like that was a reasonable choice. We have considered rat poison, but I wasn't sure how bad the smell would be if multiple squirrels died in his attic. ..... and I am SURE they would be in the areas where we can not retrieve them. Have considered trying to trap them, but not sure that is a viable option either. My son read that moth balls will run them off - but I wondered how many it would take in an attic to run them out....plus, my son would probably be living in that smell as well.

Help!.... any suggestions??? IF we can manage to get them out of the attic then I hope to repair their entry ways to prevent them from coming back in. I thought with us going into the attic and making noise they would flee - but it didn't seem to faze them!

I welcome any suggestions.....
Genna

PS I am copy and posting this on a couple of other threads since I do not have a clue where to ask for help......