New car day - help!!

[GlitteryFarts]

I've finally got the nerve to go 2nd hand car shopping today! I sold my last car in 2021 and haven't drove since eek!
I've never bought a car without help from my Dad (pathetic I know) but today I am brave enough to go to the massive 2nd hand showroom and see what's available.
I have been desperate for a car since I sold my last but couldn't afford it but now have saved enough to put down a deposit and have worked out repayments I can afford (wanting HP).
I don't even know what car I want! All I know is it needs to be petrol with decent MPG, preferably below 50k miles and ideally 2018 or above. The deciding factor will be fitting my kids in the back, 2 booster seats and a young teen, without being crammed in. I prefer small SUVs for appearance, vauxhall mokka or crossland / pergeot 2008 etc (love MG ZS but back seat looks tiny).
I have been putting this off for months, again, pathetic I know - purely because I don't know what I am doing! I have nobody with car knowledge to come with me who knows about cars, but the place I have found have over 1000 cars on site and sales people are not commission based so I am hoping will be helpful but not pushy.
Can I ask for words of advice on what to ask/look out for? What do I need to take along for finance? I'm assuming drivers license and payslips & proof of address? Is it common to drive away same day, do they give you time to find insurance? (No claims has expired so back to square one, looking quite pricey at over the 1k mark when I am doing example quotes).
I know I need to put on my big girl pants and go shopping like an adult but I'm petrified! Does driving come back to you like riding bike? I haven't even sat in a driver's seat in 2.5 years and the thought of driving home is giving me a dodgey tum! Argh I need to grow up!

We've recently purchased a new car with similar list of needs/wants, OP. We have 3 DC aged 9, 11 and 15. We went for a Kia Sportage. 35,000 miles, 2019 plate. Have half the 7 year warranty left (these transfer). We're very happy with it, and bought from a large national chain. It was more money than we'd ideally wanted to pay, but they also gave us more in part ex than we'd expected so the ball park figure was there once that was taken into account.

We didn't drive away the same day, but that's because the car was moved from one end of the country to the other for us - meaning we hadn't even seen/sat in it until the day we took it home! We could have chosen not to go ahead if we weren't entirely happy with it of course.

You can do this! The second hand car market isn't quite as crazy as it was a year or two ago. Driving will come naturally, just take your time and don't be intimidated by other drivers.

@Blossomtoes I've never had this. When you get a settlement figure it's always reduced due to less interest being paid. I've been with many different car finances such as black horse, Renault etc and all the same.