You can see in Little Dan's original picture that the gear looks, at first glance, possibly in reasonable condition.
As regard the wheels. I bought two of these locos in good condition at £20 ea S/H
I swapped the one pair of tyred wheels for the plain ones off the other loco, then used Alan Gibson wheels for that loco.
They don't have great haulage but do run reasonably well.
Both have small DCC decoders. (You need to isolate the motor brushes for DCC!)
IMHO for a 40yr old design they aren't too bad.