I would stay its a bushing. I would go through all of then in your suspension. Remember you have a 20 year old car and rubber and plastic deteriorate over time. I would also definitely shop around for another shop.
The cheap one will hold whatever pressure its rated to but it most likely break down fast and break. As for the fitting as long as the new line is similar it should work. I was always had problem putting brand A fittings on brand B hose.
To get better mileage make sure you stay up to date on your maintenance, make sure your tire are inflated to the right air presser and change your plugs. It also helps to keep your air filter clean.