What's involved in installing a FF RAS?  Do you have to remove the barrel?  

No you do not have to remove the bbl or the front sight post.

The RASII splits into two pieces.  

It would help to have another person there to help, but I managed by myself.

Actually, the FF RAS does require disassembly of the barrel.  However, you could go with the RASII like bvm mentions because it does not require disassembly.

Just to summarize:

FF RAS requires barrel  and sight tower removal as it has its own barrel nut.

RAS II anchors to the flat top and existing barrel nut so it does not require barrel or FS removal, very handy if you have a permanent FH or brake.

My bad, I did not notice he was talking about the RAS and not the RAS II.

On two Colt barrels that have seen a few hundred shots through them, the front sight tower is all but impossible to remove, the tapered pins are a pain in the ass.  I recently bought two new BM barrels with the front sight tower attached, neither would budge.  I spent 2 hours a piece cutting them open, wasting two perfectly good front sights [>(]

Agreed.  My MRE installation on a 6920 upper was no picnic, requiring creative use of a vise to press the pins out.

I just removed the front sight base from my colt barrel and it was actually a lot easier to do than I thought it would be.  Had one person hold the barrel with a front sight base resting on a rubber mallet head.  Took a 3/8" brass punch and gave it about 5 good whacks on each pin with a 1 lb hammer and the pins came right out.  Didn't even deform the pins any, so they can be reused.  Then used a rubber mallet to tap the FSB loose from the barrel.  The FSB did have a decent press fit to the barrel, evidenced by the fact that there was no carbon residue deposited between the barrel and FSB around the gas port hole.  

I have heard that the pins on Bushmasters are much harder to get out though so YMMV.  Then again, maybe I just got lucky with this barrel/FSB combo.

What is the advantage of RAS vs RAS II
as far as the AR is concerned??

RAS

mil-spec 4 rails
drop-in installation


RAS II

free floats
mil-spec 4 rails and one hump with rail
drop-in installation


FF RAS

free floats
mil-spec 4 rails
removal of barrel and front sight post required

Let's hope you don't have a permanently installed brake or flash suppressor, because that has to be removed for the FSB to come off unless you cut it open and will not be putting one back on.