Yeah you've got it right... the problem is with MTB's they tend to get a lot of punishment so things wear out relatively quickly... so it's worth going to a shop and buying new or at the very least getting them to check it out.
You could try to find a shop that does second hand bikes... as they should then be refurbed and you'll get some piece of mind that it's unlikely to fall apart as soon as you hit a bump.
.... another good thing to do is try and buy either just before or just after the new bikes come out... the older models can be got a bit cheaper (especially if the dealer has a few in stock.. he'll be keen to get rid).
A mate of mine got his Rocky Mountain full sus bike for half price!!
I'll be selling my Specialized Rockhopper before i move to Canada as i think it'll cost me nearly as much to change all the worn stuff as it'll cost to buy a new bike... and i want a full sus (with remote lockoff's)
