there are tons of yeast strains available (in liquid form), so what kind to use is hard to answer. It's essentially one more ingredient choice in a recipe. I use irish ale yeast for my stout, scottish ale yeast for my scottish, london ale for my porter.
If you're using dry yeast, there (typically) are fewer options available, but you might be able to find some specific strains in dry form... usually dry yeast packets are usually just tagged with a manufacturer name and the type; ale or lager.
How much yeast?
For dry, I would use about 10 to 12 grams. (two little packets, normally). This used to be my method.
For liquid yeasts, you *could* toss in one vial or bag (whatever yours comes in), but you'll get better results by doing someting called "making a yeast starter". Search this forum for more on that topic.... there are volumes of it here.
Personally, I would use one can of your hopped LME and another 3 lbs of DME, as you mentioned. You never know how much hoppiness is in that can, but the assumption should probably be that one can has enough for one batch. If you're a beginner, use dry yeast, but not the (potentially ancient) stuff that came with the kit. Buy some 'fresh' dried yeast... (how's that for an oxymoron?
I hope that helps....