The dealer will charge you big bucks. Since the bag cover is not offered as a part, you will need a whole new airbag. Yeah you can make up some of the cost by selling you old parts, but your still looking at 600.00 on the low side. Find. Salvage wheel from a limited on ebay or craigslist, will run you 200-250. The install isn't that bad and can be done in a weekend. The wiring will be the hardest part, you must have a aftermarket or oem radio that can accept radio controls though. The jbl or the panasonic stlye stereo will, the stock delco will not. Note the stock delco has amber numbers and unless it says jbl it will not work.
I believe "sweetmercy" had the dealer install his. I did this on my own. I actually came out ahead on the airbag/airbag cover, and the leather wrapped steering wheel with controls set me back a couple hundred bucks after selling my old one. The amount of wiring you have to do depends on the trim level you have. I have a 07 Regular Cab deluxe with the SR5 option. I had to run wires from the steering wheel connector to the K3 connector, other guys have had the wires from the steering wheel to the JK1 or JK2 , can't remember off the top of my head, and some guys have been really lucky and all they had to do was plug into the steering wheel connector, all the wiring was there.
If you're not comfortable tearing your dash, steering wheel and possibly head unit apart, running wires and finding connectors, have the dealer do it for you.
There are several threads on here describing the process, also one on modifying (cutting) your existing airbag cover to accept the controls, it all depends on your comfort level with digging into your Tundra....Good Luck!
I just completed this mod on my Tundra and it's really nice feature. I know reaching over to touch the volume control is not that difficult but I consider it a bit of a reach on the Tundra. Also I tend to make adjustments to the volume depending on what Im listening too and if someone is riding with me and suddenly starts talking. I can tap the volume down a few notches without having to reach over and say. WHat?. and then when the conversation is over I can tap it back up. Also having the Phone controls are nice too.