For London Midland (most tocs follow the same process) you'll be invited to a classroom for practical testing, Group Bourdon, Following instruction and Ticket checking their is some variation from toc to toc but the group bourdon is an industry standard. Once you pass these generally you'll have a 1-2-1 interview and if that's a pass sent for a medical. If everything is ok you'll have a company induction and PTS (personal track safety).
Training then takes around 2/3 weeks for rules, 8-10 weeks for route and traction and a 1/2 weeks for ticket/retail training. You'll also have regular exams and assessments throughout all of your training.
Training overall can take 4-6 months depending on your TOC the traction and routes you learn.
Once all this is done you are fully qualified and get to go it alone.
Shifts can be anything from around 6hrs to around 10hrs over a four day week. Hours are annualised so some weeks you may work 32hrs other weeks you may work 39hrs but over the year your average would be a 36hr week. Some local union rules may exist with shift patterns and rest days.
Although some of this may seem daunting good luck with it all.