2nd gear is one of the most common gears to loose the syncros on. Also, does it do it all the time, or just when the truck is cold? If it goes away when the truck warms up (like my r150f) than just replace your gear lube with some synthetic. From the sounds of it you should replace the fluid anyway, just to make sure there is enough in there. Also, I destroyed a clutch by not having that rubber boot that overs the shifter for hole when mud got down int here and locked up the through out bearing. So I would replace that ASAP.
If you have smoke coming through the shifter boot it could be a number of things, but you should be able to identify it by the smell. If it is exhaust it will smell like exhaust, if it is clutch it will smell similar to hot brakes.
When a clutch wears out it should make it easier to shift since there is not enough friction between the clutch disk, the pressure plate and the fly wheel to transfer the power from the engine. When your clutch really starts to go away, you can push on the gas pedal and the RPMs go up, and you don't go any faster.
