Check out This Old House...
http://www.thisoldhouse.com/toh/video/0,,20186457,00.html
The trip lever comes in various styles and each require a diffent type of repait /adjustment
The piece in the drain is screwed into the drain under the tub It is usually corroded and is not going to unscrew. You can use a sawsall or jig saw to cut the drain in 3 or 4 places around the opening and peel the piece out. You can also disconnect the drain under the tub and just leave it on the tub. There should be access to the back side of the tub. Usually a panel or door in the back of a closet that is in the room beside the bath. If there is no access, you will need to make one so that you can connect the drain to the new tub.
It is probably just rusted. Take the two bolts out holding it on and pull it up and out of the drain. Nothing will happen when you do this and it will not leak. That way you can spray the backside with some WD40 and free up the lever.
15-16 inches from back wall. 8-10 inches from side wall tub drain is on. Measurements are to center of tub drain hole. Measurements are close, not exact, and are for a standard tub.
With the two screws supplied with the trip lever waste
A right-hand drain applies usually to bath-tubs and means the drain is on YOUR RIGHT when you are standing in front of the tub.
a bath in a tub
You can access the tub drain by cutting through the ceiling below, or cutting through the side wall backing up to the tub.
Carcengenic fruit flies
tub baths are when you take a bath inside the stone in a tub
That depends on the volume/size of the tub in question. A "tub" could be a butter tub, a mash tub a bath-tub etc.
Bath tub gin
I get the feeling this is your homework ;) empty rate per minute = 1/20 bath fill rate per minute = 1/12 bath find t= minutes to when bath is full, 1/t bath (combined empty and fill rate) so 1/12 - 1/20 = 1/t solve that for t and you have your answer in minutes ;)