Originally Posted by RegularGuy
You'll need to replace your bottom bracket, front derailleur, rear derailleur, crankset, and at least the front shifter. Might as well toss a new chain on and replace some cables while you're at it.
It won't be cheap.
I suggest you call your LBS or check out some of the online vendors to find prices.
I don't understand why he'd need to replace either of the shifters. Certainly no need for the rear, and I thought the new Shimano front shifters were all double and triple compatible.
You might first want to try riding a double with a 12-27 cassette. Big change from the 12-23, and the shifting on the front mech is much nicer with a double (at least it has been on all the 105 & Ultegra bikes I've ridden).