You can take the instructions you got with the kit with a grain of salt. One can't put a specific timing on fermentation. However, 2 weeks is about right for a typical lager primary fermentation (which would include diacetyl rest).
If you do a diacetyl rest (which you probably should, especially if you started fermentation warm), you only need to allow the temperature to go up to about 60-65°F. This rest is done when the beer is still in primary as fermentation is winding down.
After the diacetyl rest, you can slowly cool the beer back down (5°F per day) to below 50°F. You should really transfer it into a carboy or Better Bottle. A plastic bucket may allow the beer to oxidize. Then lower the temp. down to the low 30s°F (32-34°F). Lagering times are dependant on OG and how dextrinous the wort is. A typical lager would lager for about 7 days per 8 points of gravity. So, a 1.048 lager could lager for 6 weeks.