I'm new and I don't know what I'm doing!

I'm 15 with a 1999 Honda Foreman 400FW. I bought it for $600 with 10338 miles. I had since I was 12. i bought from a guy who litterly beat the S**t out of this quad, It has been on 15ft tabletop jumps, mud up to its handle bas and a tractor had to pull it out, rolled down a hill so bad that it bent the rear sub-frame (still bent) and it was no lie round, and reverse wheelies have been done(that's why I still don't have 4WD. The best part is that it's stock, never been rebuilt and it still runs like new just doesn't look new. It broke about 2 weeks ago. I didn't know that there was a bearing and seal missing on the left axle tube and rust from over the years had gotten in there and rusted the axle shaft and I stripped out one day. all the seals and bearings look like they haven't been done in years. I already had spent $400 alone on the front end between bearings, boots, and shafts and couplings so i had a tight front and 4WD I still don't have 4WD yet because of the diff bearings so I put it back together without the front diff and then six days later I strip the rear axle shaft. Can anyone help me out with a used axle shaft in good condition or maybe a ring gear with good splines. Also why do our quads hold there value so well (over $2000 on ebay) is because there **** near the best built quads and won't take no for an answer?