You say you are a "beginner" when it comes to atvs but what about engines in general?
If you are mechanically inclined, have a decent set of tools, a factory service manual AND a decent, clean place to do the work....dig in!

But you must also make sure that the lower end is in good shape and not contaminated with muddy water. Does no good to redo the top end if the bottom end has remnants of muddy water in it.

If you don't feel capable of doing it, check around with friends or family and see if they can help.

But please get a service manual....no sense in going into this blindly.

 

You will need to get a FACTORY service manual (don't waste money on Clymer's, etc) and a good torque wrench for sure.

If you sucked in a lot of mud/grit into the cylinder, it will wreak havoc on your rings and thus cause the oil to blow right by into the combustion chamber (thus the smoke and oily exhaust pipe) The grit suspended in the swampwater inside the cylinder would settle into the rings, and then it would grind itself into the cylinder walls with every cycle.

What you might consider doing is pulling the spark plug and looking inside to see if there is any dirt and/or damage readily visible. One time after a muddy water immersion, I was able to save myself a ring job by pulling the plug, turning my ATV on it's side to where the sparkplug hole was at the bottom, and using a small diameter hose, wash the dirt out of the cylinder, first with water (hot is best) and then a LOT of wd40. It may be too late, but it's not expensive to try

Even taking the head off will require the manual and the wrench, so don't try anything until you have both.

 

is there anything i can do next time to prevent this and would i need to replace the valves and pistion or just the rings and gaskets

 

You will need to have the piston and cylinder inspected and measured to determine if they are useable. I doubt the valves are hurt.

Snorkel everything, or avoid going into water that deep to keep grit and dirt out of the crankcase.

 

pk the only reason i was asking was because of the bike back firing when down shift and when i turn it off after riding

 

Yes the oil is from your piston rings and cylinder,dirt and rings are not good mates.From hand on experience and advice from others,pull the engine and split the cases,do a complete cleaning,you would be surprised where you will find the muck hiding,even in the clutches.A top end job is a bandaid.I've seen guys do a top end job, 2 weeks later or less they are smoking again,several hundred bucks wasted,when spliting the cases does not cost much more,just gaskets and Hondabond.I've tore one down last year brought to me for a top end job ,the guy run a case of oil through it along with some sort of motor flush and said he got all the silt and dirt out,I convinced him to split the case and got a half of a coffee cup of silt/sand out.A repair manual would be handy if you have never done it and you will need some pullers if you do a complete teardown,I'm sure your local Honda dealer will pull them for a small fee if that's all they have to do.When you get it back together don't be alarmed if it still smokes when it warms up,your exhaust is still full of oil,it will burn off eventually.