My Dog gets so excited going to PARK - cries all the way, I have tried to make him sit before we go out to which he is very good at,however its like he wants to be calm but the excitement makes him nervous and it a real battle

Is it only when you go to the park you have this problem or is it every time you leave the house?

Getting him to sit is a great start.
I teach my dogs to watch me, when you say the command "watch me" or "watching" the dog ONLY focuses on you.
To do this you start at home and use the dogs favorite treat or toy and get them to look at it/you.
Repeat the command "watching" while you are doing this.

After a few tries get someone to cause a distraction. The dog will want to look way to see what it is but you have to regain the dogs attention with the treat and get him to focus on you again.

Once the dog is good with watching you with small distractions move up to larger ones. Get someone to rattle food bags or squeek a toy, something that will really make him want to go.
If he attempts to go or breaks eye contact from you then just hold him and make him sit again and repeat the process.

Eventually you can build up to doing this on the street and during walks.

It does take some time but it is very effective.

There are also some harsher methods which include snapping on the leash when he pulls or cries but I personally don't use them as I know some dogs who have become fearful of the lead this way.

Dogs can associate certain actions with certain results. Obviously your dog EAGERLY looks forward to going to the park! Put yourself in his place... what do you get this excited about doing? What is it about this 'thing' that is so exciting to you? Your dog is not that much different. Can you see anything that is particularly exciting to him at the park? I could be just the park itself. There are all sorts of different smells for a dog... other dogs, people, and who knows what else.
It is possible you have created this yourself by going to the same place all the time. He knows what to expect and looks forward to it. If this was the dog groomers, or (for you) the dentist, would either of you be so excited? Vary your walks, or whatever. Go somewhere else, or take a different route. Break the habit pattern. Don't give up on the park itself, but just give it a rest for a while so he doesn't know what is going to happen other than just 'getting out of the house'.
Some sort of obedience training always improves a dog's 'manners', but is not something you can simply read about and do. It almost requires some demonstration as well as instruction. Many communities have classes periodically, usually at a reasonable price. Obedience doesn't mean teaching a dog tricks, or special behaviors. It basically teaches them how to behave on a leash. Once that lesson is learned, a learning pattern has hopefully developed and other things can be more easily introduced and learned. Obedience training is an on-going process, and probably never really stops... not too different from raising a child. It too has a point where nothing seems to be getting through.
Hope this helps, and good luck.