Sounds like you could use some help (duh!). I suggest that you go over to www.johnbridge.com and look in their "liberry". You can ask questions after you read the help there on building a shower. Note, you drain line may not be big enough to pass inspection. A shower generally requires a 2" drain line, your tub MAY have a 1.5". As to the drain height, most of the clamping (clamps to the waterproof membrane) have a height adjustable fitting. You worry about the height after you get the shower pan installed and the guts of the drain assembly installed. Finally, it is usually ackward to have the drain close to one end of the shower pan - it works and looks much better normally to have it centered. All of thatis covered in the "liberry" on the site.