I first want to say that when I looked at all grain brewing from an extract brewers perspective, I too thought it impossible. But since I did my first all grain, I haven't looked back. It really isn't that much more difficult but does add probably about 3 hours. The thing an all grain brewer is doing that an extract brewer isn't is pulling out the sweet wort from the grains rather than using extract. I like just buying a mash/lauter tun. You can mash easily right now by just putting in 10 lbs. of grain and hot water into a cooler to get a mash temp b/w 150-155F. Let it sit for 1 hour. Then you need a lauter tun with holes on the bottom for the grains to settle out. You'll pour hot water (168-170F) over the grains, slowly for an hour. Wha-la! You've got your wort! I lauter out about 6.5 gallons and boil in a 7 gallon pot so I don't have to add water at the end. Once you get this process done, you'll find tons of new toys to add to make your beer better and better. But I promise you, once you do all grain, your first beer will be so much better than all your extract versions (although not to insult anyone; I personally have never made a better extract beer).
Overall you'll be adding about 2 1/2 - 3 hours to your brew day (1 hour mash, 1 hour sparge/lauter and 1/2 - 1 hour of getting liquids to temps).
2 of the many suppliers where you can buy cooler mash/lauter tuns for under $150. http://www.homebrewstuff.com/index.php