BOAC,
This getting to be a "how much is your time worth" scenario!
How much time are you willing to spend (and what's your time worth - what else could - or should - you be doing?) for an ageing 76GB drive in a dodgy USB caddy that you could replace for £50 with a 500GB unit!
I use this rule of thumb at work a LOT - if it costs £X to buy, but a multiple of £X in hourly cost to have someone fix it, just go and buy it! Of course, it is never my money involved.
SD