As regards your gearbox, I have had the same thing happen. The cause there was gearbox oil leaking out through the powersteering pump. As I drove along, the oil would gradually disappear and subsequently the level of oil would be too low. The lights all came on on the dash, resulting in no gearchange. A top up of oil fixed the problem immediately.
I have since had the powersteering pump overhauled of course. Cost : 250 Euros. Cost new (so I was told by the mechanic anyways) 600 POUNDS !!
