Am starting college in Febuary and i'm 30, like you its a massive career change. However the age thing does bring some benefits
1. Its a big decision, and i've taken it in the full knowledge of the risks- i'm not going to tail after taking the risk!
2. Having spent almost 18 years in education, and then spending another 10 working my arse off and learning at work- the learning thing isn't a worry- just another skill to regain.
3. You will have dealt with stresses and strains in life already- at 30 you are far more confident than at 18, and certainly more mature
4. Passing interview will be WAY WAY WAY WAY easier- all the older guys at interview found the questions much easier than the younger ones!
Our age its already quite hard to career move- its already a HUGE motivaiton for me- you will do ALL you can to amke sure you pass!
Go for it and stop worrying.