assuming your tank is still up and running, here's how I'd handle it....I just did the swtich in my 55G.
1.)First step is to train your tank leaving just enough for the fish to be able to swim around....
2.) Move fish into a 5 gallon bucket
3.) drain tank as best as you can
4.) scoop out all of the old gravel, holding on to some of it (more in a moment)
6.) rinse your new gravel over and over....i washed 75 pounds of gravel about 10 times....this will save alot of gunk going into your filter
7.) add the gravel....you mentioned you only have 5 pounds of gravel, thats gonna be spead pretty thin on a 10G tank...most aquarists reccommend a pound per gallon atleast.
8.) Re-fill your tank, trying best to match the temperature of your tank
9.) Add fish
I would pick up a mesh bag, some people use pantyhose....and place your old gravel in it. You can then put that bag of gravel in your tank, in a high current area, this will allow some of your old seeding bacteria to remain a part of the tank....personally, I just put mine inside the filter chamber and let it run in there for a while.
if you water changing and there is still fish poo on the gravel, I'd reccommend picking up a gravel vac....which is undoubtably make changing the gravel out alot easier...
Hope that helps, others will be along!