You are correct about the lamp life being limited on laptops. However, the rated life is quite big, generally around 20-30k hours. That is between 2.25 and 3.5 years of continuous runtime (24x7x265). At normal usage, say four hours a day, five days a week you could expect somewhere around 19 years of life.
To answer you second question, yes, you can replace the LCD assuming you can find the replacement parts. If you have to send it back to the manufacturer, you should probably just buy a new laptop. A 15" LCD screen (the bare screen) will probably run you around $500. Expect to pay $750-$1000 for the screen plus labor if you have someone do it for you. And unless you are really comfortable with doing the work, I wouldn't recommend doing it yourself. It's a really expensive oops if you mess up.