Can anyone give me solid tips and advice to killing the chameleo

As I'm sure you already know is turns invisible, to stop it from doing that you can shock it or flash bomb it, another way is to do alot of damage to it's horn and it's curled part of it's tail. This will temporarily stop it from hiding. At 25 minutes it will flee to a different area(for example if you are in the forest and hills it will go to the swamp)where it stays and you can kill it there cause it will not run to a different place. You will have to wait for the quest to change. As for the problem of it killing you before you can heal you just have to get the cooking skill, witch lets you eat and drink faster. The only armor I know as of now that lets you do this with out decorations is a full set of Tigrex armor. Oh.... And by the way if you can cut of it's tail it will all but rinder the over grown chameleos visible. Happy hunting, good luck, and godspeed.

After 25 minutes it will move to a different place, shock it to keep it from going invisible.

It only leaves after 25 min only if youve damaged it enough, thats the limit for the quest, so you don't kill it.
If you don't want to get hurt badly during the quest, id suggest using a bow, maybe a hunters power bow | or ||, doesent matter.
Keep hitting it in the horn, until it breaks, when he goes into rage mode, he will turn visible so you can see him for a while, but after that, he turns invisible.
To stop this from happening, like warrior said, you can use a flash bomb, or you can make him stagger when he starts to shimmer, this will make him visible for the time being, for at least 8 minuets.
You can also do this without the tigrex set, I did it with a full remobra set and a kirin horn (helmet).
As for the healing problem, if you train with the bow, you wont get hurt very easily, becouse his attacks are slow, and if you keep your distance, he absolutely cannot attack you, but if he does, then get back to where he can't hurt you, and heal then.

Btw if you hit him in the head with a rapd shot when he jumps up and sprays poison, he'll fall giving you an extra chance to attack.

I also use dual swords I try to avoid attacking from the front and go to the right back leg and devil dance on it(when it falls it always falls onto the left leg) and keep making it fall over and cut off the tail and smash it's stomach. If possible try to use a fire weapon. Use your cats to get extra health and bring along mega armourskins and demondrugs.