Whether or not it's a lager depends on the yeast, but if you ferment a lager yeast at 20C, it won't taste much like a lager. A good practice for pale ales (and German alt/kosch) is using a clean, neutral ale yeast and fermenting at low temps (18-22C). This prevents off flavours from coming in. These beers are usually cold-conditioned for a little while too, to clean them up even more. This may be an option for you...
With priming, DME is definitely not the same weight as dextrose/corn sugar, as DME is about half as fermentable.
Look at
http://hbd.org/recipator in the carbonation calculator, you'll find all you need.
Racking to secondary, the yanks are adamant that siphoning is the only way and plastic fermenters are the devil, but what I do, and what works every time, is just draining from the tap/spigot in the fermenter... works every time, and if you pick up a bit of yeast it doesn't matter.
A week is a bit short, you should make it more like 2-3 weeks, but a week would be ok if you're putting it in the fridge, for example, or if you just want it to finish fermentation.
Edit: I think the yeast you get in the Coopers kits is an ale yeast anyway. Stay away from lagers unless you have a temperature controlled fridge... I won't scare you with what you have to do, too much information to take in, it's not as simple as keeping them colder.
Anyway, off to work.