I have done it on a T400 which is very similar.
I had a lot of difficulty getting a caddy tho. A lot of firms wont ship to the UK ! From Lenovo here it would be £60 which seemed a lot when they were £20-30 in the US. Eventually I plucked up courage and bought one from China which I was very cautious of because it was so cheap.
It arrived in 7 days and fits perfectly and works perfectly so I am really happy. It cost me $9.98 and an extra $2..00 for express posting but you wouldn't know that it wasnt a genuine part ! It is shepd to match and has a blue light to indicate use. They make them for all models and if you arent sure then the guy there can tell you which model you need... I dont know if I'm allowed to do this (sorry admin but I'm new) on UK ebay they are parts-wholeseller. just I spent ages searching and if it helps someone else
ohhh its hot swappable and far faster than a usb caddy and you can boot os off it too..