Unless you are doing major remodeling, the drain may have to be assembled before the unit is set. In that case it is very difficult for a first0timer to do it. Get a professional, because you will probably wind up with one anyway, and if you make too many revisions before he arrives, it may make his job very hard and very expensive to correct what you did. Also, do you have large enough doors and sufficient room to get a one piece in and turned into position? : We currently just have a shower stall in our bathroom, but we are planning to install a bathtub with shower (probably a one piece). The shower stall has a cement floor – the drain is centered. We need to move the drain closer to the wall to match the bathtub – how do we calculate the measurements and is it as simple as cutting off some pipe – or will we have to replace the pipe – should we have a professional do this as we have no experience with plumbing (cant you tell…) Thanks ahead of time!!