Both Lowe’s and Home Depot offer bathroom remodeling services. Home Depot remodels cost $5,000 for a powder room up to $30,000 for a master bathroom remodel. Lowe’s suggests that customers expect to pay at least $100 per square foot on bathroom remodels. Both stores offer repairs on your existing fixtures and installing upgrades or new replacement parts.
Having an onsite dumpster should be your responsibility if it is something you are going to demand. They aren't cheap. Make suggestions or request a dumpster be included in the bid, but I would never start demanding anything when requesting proposals. They may have their own suggestions. We own a dump trailer and we bring it during demolition to handle the large debris. We have the trailer to avoid having to rent a dumpster on the job. If asked we can share this information, but if you require a dumpster instead we would have to take the time and research getting a dumpster to your house and add in costs we aren't accustomed to adding. That takes time and effort we may just not want to expend to give you a quote. Good contractors are generally very busy.
I acted as general contractor and did all my own demo to remodel my 6x8 bathroom. I hired subs individually to do most of the work - an electrician, a plumber, a drywall guy and a tile guy. I painted the walls and the ceiling. I replaced everything except the cast iron tub. Materials and fixtures cost around $2000 and labor was about $3000. My subs had no problem with me supplying the materials, because I discussed their job scope in advance. This project took 6 months but I did have another full bath to use in the mean time.