Another Outdoor Outlet

I've got an old Pacific Federal box and I was going to run some electricity to my shop in the back, but the breaker that I need, or that I was told I needed, a 100 amp breaker, costs $220.00 The guy I talked to said that Pacific Fed went out of business and now they no longer make these parts, hence the price.......sooooo, I was wondering how much an electrician might charge to install a new breaker box for me. I know absolutely nothing about electricity, so this isn't something I feel like doing myself. I want to run 220 from my breaker box in the garage, up through my attic to the other side of the house, then out and down into the ground and run it about 50 ft to my shop. From what I was told, I needed 6 ga wire in 1 inch conduit when the wire enters the ground, but I need steel conduit from the ground up and also through the attic. Does this sound right, roughly???LOL I told you I don't know alot about this stuff... All I want to do is get the wire fed through, then I'm gonna have an uncle over to connect it for me...he's kinda old, and I don't want him in the attic or outside for very long, so I'm trying to get most of it done before he comes over....sorry for the long post!! Thanks for the help!

Our house is 23 years old. We have owned it for 6 years. One detector which is wired into the house has suddenely started ringing when the bathroom steam hits it.... it is located just outside the bathroom door in a small hall. From what we can determine there is no backup battery in it. Advice/suggestions appreciated.