Designing Kitchens and Bathrooms - How can i install the plumbing for a shower drain

Hello, this is my first post on DIY I have a pretty large project i will be atempting to work on over the next couple of months. I have a studio that was half completed most the plumbing was put in prior to when i showed up. In the bathroom i have already removed the old toilet and i realized the floors beneath it were rotting out so i removed the floors and i can see the sewer lines beneath the floors. There is a hole in one of the sewer lines that looks like where i could connect pipeing for a shower drain. (this could of been done intentionaly by whoever did all the work before me) My idea was to take pipeing and use it to connect from this hole up to around where the base of my new showers drain would be. Im not sure what type of pipe i need or if this is the proper way to connect the shower drain. Also im a little worried about how im going to have access to the underside of the house. there is no crawl space so having the floors torn out beneath me would be my only access point. So i figured i could wait to replace the toilet and replace the floors beneath the shower while still having access to hookup the plumping and put the bottom peice of my pre-fabricated shower down. Does this sound like the right way to go about this? I havent been able to find much information on installing the actualy plumbing needed to connect to a new drain. Also the sewer line was made outta steel or similar metal. Would i be able to connect PVC pipeing for my shower drain? Also if i were to call a plumber to do this for me how much do you think they could charge.

Any help or sudgestions would really help, i can hopefully post some pictures soon if needed! Thanks so much! :)