Hire an architect to prepare plans and specifications so all contractors are bidding on the same work.

Talking about reasonable price, in Palo Alto, with contractors, architects, bids, etc. etc. No way. Sorry to say that I think you will end up paying more than you expect. Nothing is ever as simple as it sounds and there are always "reasons" why you will end up paying out more than even the agreed price. For some reason, an architect will have to change something after the deal is made and the work has started, which means that you have no choice left and then when the city gets involved, they will expect things to be done somewhat differently. Good Luck.

When you open up a wall you are often surprised. If you want to pay an architect to open up all your walls so she can be sure of conditions, do so, but usually it is cheaper to go with the educated guess, then pay for surprises.

I had this done a few years ago on my old house. It was not a big deal. You also want to look into bracing cripple walls. You certainly don't need an architect, you just need experienced "earthquake retrofit" people to crawl around under the house.

That said, within a day after the work was done, it turned out that one of the workmen had whacked the gas burner of an old floor furnace, probably when moving a cripple wall bracing board around, and I was lucky the house didn't go up in an explosion. When I contacted the earthquake guy later, he denied his people had done this.

Anyone can make a mistake, but the workman covering it up, particularly when it was a dangerous mistake, and the owner then denying it was unforgiveable. (They also whacked the door into the cellar, but I saw that happen, so they fixed it.)

I would tell you the company, but I don't want to get sued. I googed and found this web site that may be helpful. www.abag.ca.gov/bayarea/eqmaps/fixit/fixit.html
Follow links in there and you will get to contractors. The fellow I had the problem with is based in Menlo Park, and since there are several listed in Menlo Park, perhaps I can give you that clue.

Would you have an appendectomy without a diagnosis?
Contractors will give you an estimate, but an architect will give you bid documents that, among other things, require the contractor to have a bond and proper insurance. When the contractor "discovers" something that will cost more to fix, the architect can evaluate the contractor's assessment and price. A low bid without professionally prepared specifications is an invitation to trouble. I had a garage replace a $200 component on my car and my trouble was not cured - they then found that a $20 switch was the cause.
Call the local AIA for recommendations.

Would you go to a doctor to have a bandaid put on? We're talking about some bolts and some sheets of wood in a well-understood process.

yeah, I have to agree, an architect is overkill for this job.

Be sure, then, to get a building permit.