Clean the 8mm by hand using powerful chemicals (Google it; I used the product Goo Gone). The film emulsion is incredibly strong, but will probably have picked up mold and such over the years which you have to physically rub off. Film contains an incredible amount of information. i.e., quality and it;s worth the work to bring that out.
I used a commerical house for an hour of footage at $400. They used a sprocketless telecine machine. They offered a manual color correction option , in which an operator sits by and corrects as the 8mm rolls. That was another couple of hundred so I declined. The result mini-DV tape I received was disappointing. It was washed out and the colors were terrible. I used a reputable house and I live in Los Angeles, where folks are supposed to know how to do this stuff. Given the expense, I would ask for a sample of your footage from any pro house before committing to a large payment.
Subsequently I began making my own transfers (Google it). Basically you just video a small projected image of your film. The problem to solve will be flicker, and the flicker will depend on your equipment. Adjustable frame rate projector is good. I don;t have one.
Unfortunately, my digital camera makes a hash of recording projected film. The flicker is profound. However, if I use an old analog video camera to record the projection (on white or off white paper, not a 1950s-era "move screen", with reflecting surface) , the flicker is hardly noticeable. Then I convert the VHS-C to DV, camera to camera, and load the computer from there.
8mm and S8mm were superb media. It's all still there if you can capture it.