Just bought my son a 400EX and it looks like there is some stuff that needs guarding. Where is the best place to get skid plates. Should the A arms and belly be guarded as well as the sprocket and disk ??

 

The stock skid plates are alright if you don't ride that hard. Other than that the back bends up into the disk brake and thats not good. Here is a link for some of the best skid plates you can buy.
http://prm-atv.com/

The swing arm skid plate and the full coverage you need and if you have the money get the a-arm skids.

 

I bought a plastic one from a person on e-bay for the chassis. It fit great and is holding up extremely well. He was a great guy to deal with, very nice e-mails and very fast shipping. I put 22" swampers on the back of mine and noticed a huge improvement on the swingarm hitting rocks, but I am probably still going to get a swingarm skid. I have really only heard good things about PRM skidplates so that is probably what I will get. I would definitely recommend a chassis skid plate if you do woods riding a lot, helps roll over logs.
Exer

 

the plastic one you bought was probably a maier, they are nice looking and made of a harder plastic, new i believe cost around $40, i ride hard in the mountains in rocky areas and havent had any problems, they get scratched up you dont really have to worry about it since it costs a 1/3 of a aluminum one i believe, if u get a deep scratch just flip it over and bolt it back on... just gotta decide on what u think is the best for you

 

Thi guy makes the skid plates himself and sells them on e-bay. I am still waiting for him to make one for my kids blaster. He has made them for warriors, 250r's and the 400ex, possibly more.
Exer