Lacing wheels

It can be difficult depending on a few things.. Quality of spokes and quality of rims. I've laced new wheels with good quality spokes without a hassle. Theres plenty of 'how to's' on the web to follow. Its not that hard, just be patient. If you're working with old or mismatched spokes and crooked rims it might be a job for the pros. Just my 2 cents. You can't loose having a crack at it.

With some basic tools and some patience its easy.

if you are swapping rims make certain you count how many spaces apart on the rim are any two spokes that sit next to one another on the hub. Make sure you write this number down so you can easily repeat the same pattern. I personally avoid using power drills to do up the spokes as some do up easily and some may not (if relacing in a used wheel). True the wheel by inserting the axle and hold the axle in the vice allowing the wheel to spin to dial indicator mounted on the bench. I just use anything that will sit still on the bench and move the wheel close in the vice.
True into and away from the hub first and then true the rims side to side movement last. Only other advice I'd offer is that older slightly corroded or dirty spokes dont make the job easier and bolt cutters work great if replacing the entire spoke set.

Lacing an 18 inch rear hub to a front rim ?

You would have to make certain that the 2.15x18" rear rim (I am assuming you'd use an FE rim) would give you the tyre selection you needed before you worried about whether there was a spoke that suited.

SM fronts are are 3.5x 17" so the spokes from an FS wont do the job. If the diameter of the rear hub is the same as the diameter of the front hub AND the width of the hubs are the same theoretically rear spokes would lace a rear rim to a front hub. This would give you an 18" front and an 18" rear but again I would advise a thorough investigation of what tyres you can get that would be suitable for the job at hand.

A few of my thoughts when lacing wheels are:

• 
  Don't do it all at once, one or two turns at a time, and when they are taking up the slack, smaller turns
  Lube all threads and under the nipple heads with anti sieze.
  Know where the rim centre line is supposed to be and reference that from your jig
  A swingarm or forks are OK as a jig
  Spokes work in tension, not compression
  Loosening/tightening left and right spokes together moves the centre of the rim, ie radially
  Loosening/tightening left and right spokes adjacent moves the rim laterally
  With care, thinking about the above, I can get a rim to less than 0.5 mm run out laterally and radially

Can sombody explain to me the difference again between traditional and non traditional rims/hubs, I know i can send out the hubs to buchannons or somewhere to get relaced but id still just like to get it together myself also to keep down costs, the local bike shop charges a minimal fee to true a wheel, or at least thats what they told me, if i cant get it myself with the dial indicator.

does the rim i get have to be a non-traditional rim to match my non-traditional hub?
can i just order non-traditional spokes for the rim size i want and get a traditional rim?
are ktm rims non-traditional?
can i recut and rethread my spokes to a smaller rim size?

i cant beleive i still dont understand whats so hard about this relacing thing, maybe i just need to get my rims side by side with a tradional rim to get it.lol.

Yea i thought about the alloy wheel route but i hear they dont like it when you go up/down stairs, drops offs, hit curbs, jump ditches etc. they can look very cool if done right but im not going to risk breaking a rim if i can help it. i also couldnt deal with the rims rotating the wrong direction, i am way to OCD for that :? i just realized my wife just got a dirtbike again, im gonna go compare our spoke patterns and see if i can make sense of this, its a yamaha i assume it would have traditional rims.

does anybody know approximatly what kind of costs one would look at to have our hubs relaced to 17"s? just how eexpensive is it?

I don't understand the term 'traditional'. Do you mean the type used on the older Bergs like my 98, and older Euros generally, that had the spokes going in the opposite direction to the current ones? If so, I guess that's your answer. Some also had 40 spokes vs the current mostly 36.