The 318 is a nice tractor, powered by a gas Onan. If you are interested in this vintage tractor, also consider the 322 and 332. They have a three cylinder yanmar engine in them. 322 is gas and 332 is diesel. Both are good engines, water cooled and have a good life expectancy. Though the 322/332 were no where near as popular as the 318, they take the same attachments as the 318, and share many of the same tractor piece parts. This allows you to at least draw from that stock on both the JD Parts side, and the used market.
The unit mows good. I agree that the mower deck belt routing is a pain, and I seem to get it done ok - but I always seem to be swearing as I am laying on the driveway getting the deck hung and belt routed.
Tillers for these units are available used, but you have to look around. The big thing to look out for with a tiller is they need special mounting brackets. A pair on the rockshaft and a lower pair that mount on the "frame". Many times people forget to take them off the tractor when selling, and the tiller and brackets get separated. Since the brackets are no longer available from Deere, you have to be careful you get the tiller with the brackets.