try this web site http://techdocs.shimano.com/media/techdocs/content/cycle/SI/Tourney/RearDerailleur/SI-5V80A-En_v1_m56577569830612967.pdf
Shimano Tourney is a model of front and read deraliers, not a bike
Depends on what the trouble is. www.sheldonbrown.com, www.bicycletutor.com or www.parktool.com can tell you all about it.
www.sheldonbrown.com and www.parktool.com are 2 excellent sites with maintenance tips and instructions
It's got Shimano 3x8, Acera. Entry-level stuff.
you have to buy and install adjustable cam gears. but if you adjust it improperly you will lose power/gas mileage.
Shimano's population is 7,003.
Shimano's population is 975.
Shimano was created in 1921-02.
Shimano.
Sure. There are two things that has to match, the number of gears, and the actuation ratio or the rear derailer. If the rear derailer is a Shimano, then it'll take a Shimano shifter no problem. If it is an SRAM derailer, then you have to figure out if it's the Shimano-compatible version or the 1:1 pull SRAM version. If it's long-pull SRAM, you'll need a long-pull SRAM shifter. Once that's sorted out, unhook shifter cable at derailer. Pull grips off bar, loosen pinch screw(usually Allen head) slide twist shifter off. Slide trigger shifter on, tighten pinch bolt. Slide grips back on. Install shifter cable. Adjust shifting. Done!
Shimano Nexus was created in 1995.
Argos-Shimano was created in 2005.