A bit of help for a confused newbie, a clock (and probably a stupid plan)

Hello.
Ill start off by saying what i would like to achieve and take it from there..
I have a truck with an analogue clock that i would like to replace with a digital one.
At first i tried looking for clock that i could modify to fit into the space of the analogue clock but i couldn't find anything. So i decided to try and make one, and the good bit about that is i can make it so it fits perfect. I really like designing and building things (I practically live in my workshop) but most of the stuff i do is mechanical. I do work with electrics but i have never built anything like this before (semiconductors and the like).
I have done quite a bit of reading regarding how to build a digital clock (TTL) but there are a few bits i don't fully understand. (apart from basic electronics everything i know is self taught)
One thing is the voltage. The truck is 12v. Can i just use a 7805 to transform and regulate it to 5v?
Second thing (the one I'm most confused about). What should i use as a timer? Is it possible to use a 32.768 KHz quartz watch crystal? If it is, how do i convert this to 1 Hz using decade counters (74LS90)?
Any guidance or thoughts would be very much appreciated.
Thank you.

You could use a 7805 to regulate the voltage.

If you divide a 32.768KHz signal by a 15 stage binary divider you will get 1Hz. A circuit such as the CD4536 can provide this required division. It's input can also be configured to operate as a crystal oscillator with the 32768Hz crystal.

But building a clock from scratch is not trivial. Perhaps a module such as this **broken link removed** would simplify the task.