What is involved to recharge the Air Conditioning System? I believe you need a machine to do it, so I am guessing you can't do it yourself.
Short answer it's not a DIY project. There are many things that need to be checked, specialized equipment, and a mistake can cost you a lot of money.
It's against the law to work on AC without a licence in some areas, so check local laws and regulations.
There are many reasons the AC is not cooling and a little low on refrigerant is one of them. Topping off the system with a DIY can might work. The cars on the road to day are less forgiving to over/under charge of refrigerant. Being off by as little as 3 - 4 oz is enough to have a major performance hit, or no cooling at all. Too much refrigerant will damage the compressor as well, this can be a slow death so you may not even realize your recharge caused the compressor failure.
Refrigerant Oil - Even with the correct equipment it can be difficult to get the oil amount correct. Too little you burn up the compressor, too much can affect the performance or damage the compressor. Using the wrong oil can also damage the compressor. If it's a hybrid with electric AC really don't mess with it,the cost of those compressors run in the thousands and are easy damaged with the incorrect oil.
AC systems don't use up refrigerant and if it's low there is a leak. When refrigerant leaks out it takes oil with it, so if you keep topping it off without added oil you'll damage the compressor. Some of the cans have oil in them but that might give you an overcharge of oil leading to compressor failure.
As for this guy, I'd stick to more reputable sources for automotive repair.
It's a good idea to service your AC system on a regular basis but recharging it every two years is excessive and a waste of money.
Basically it depends whether the system is empty and needs to be completely vacuumed and refilled or if you just want to top it off.
If you want to top off the system you can probably just purchase a kit from your auto store and do it yourself.
If the system is completely empty just take it to a shop and let them handle it.