generally, depending on the screw type, you should use a powered screw driver, they have lower torque and generally lower voltage. you dont want to strip screws.
sears has some cheap drills. i have a 16.8 they had on clearance. they work fine, as long as you dont use it for a job. dewalts are great for the job. if you can, try it out, some drills are quieter than others. and as for the weight, the higher the voltage, the heavier. and metal bearings are a good thing.
anyway, get a kit that gives you 2 batteries and a charger. and 3/8" chuck is standard. get a set of drill bits and screw driver bits with magnetic bit holder. if you have plans on cutting metal, get tungsten carbide bits. dont go wild on those 1000 piece sets or what not. just get the basic sets, and what you think you may need later. and then buy as you go. a small socket set may do some good too.
a 9.6V or 12V drill is fine for small jobs such as drilling soft materials and screws. but, go as high as you can for masonry.