What you want to do is indeed a really good idea. Full boils, as they are called, are preferable for several reasons:
1. You get better utilization out of your hops and therefore have to use less of them. Saves money.
2. You get a more accurate gravity reading before you pitch your yeast since the sugars/starches are evenly distributed throughout the wort.
3. Your wort will darken less during the boil.
However, there are a few obstacles to overcome in order to do a full boil:
1. You need a large pot, at least 7 gallons. Remember, you will have to boil more than 5 gallons in order to end up with 5 gallons at the end of the boil. And, unless you use Fermcap or something similar, you need some headspace so the pot doesn't boil over.
2. You need a fast way of cooling the wort. Sure, partial boils you can cool in an ice bath. But, you have a lot more stuff to cool now. That means an immersion chiller, counterflow chiller, or something similar. You can also stick it outside in cold weather in a large drum filled with water, much like you would an ice bath. People have had success with that. That will only work during the cold months of the year, though! And, depending on how full your pot is, it can be a really bad idea to carry around 5 gallons of boiling hot wort. Having that slosh on you can cause some pretty nasty burns.
3. You need a heat source that can bring 6 gallons of wort or so to a nice boil.
4. You need to adjust your hops or else you'll end up with a beer that is much more bitter than you wanted. The easiest way to do this is by using software such as BeerSmith or ProMash.