BoT

the difficulty really depends on the complexity of the setup.
the features and pieces are involved the more complex it gets and therfore the more difficult it gets. there are some decent all-in-one products out and some good entry kits
for moderate ocerclocking i might would not put forth the effort but if you want to take it a little further then i think that would be the way to go.
no doubt there is a learning curve to it but it is a very interesting one.
be warned thou, h2o is addictive and can get heavy on the wallet :)