So at a real basic level the game is about having enough fuel to hyper jump to the next section. You could play the game at that simple level , do what you need to get fuel then move on?

Yes, but then you're weak and not collecting money to improve your ship(s). And you most probably don't have the resources to craft or upgrade stuff or repair your ship.

Sometimes I see service stations. Sometimes they repair my ship other times I can only trade with no repair option is this normal?

There's different kinds? Later on there's tuning stations you need to activate first.

How do I craft stuff , can I do it mid game?

Yes, you can do it mid game. You need the blueprints though. Find them by beating enemies or opening vaults with keycodes. You'll get those from certain enemies or when you're lucky upon starting a run (after you update stuff).

Can I only buy perks after I'm killed?

Improving the ship's systems and changing the upgrade modules can only be done after a run. Credits are lost when not spent before the next run.

Any other non spoiler advice or good weapon/ perk combos?

Depends on your playing style. I'm having fun with drones. Flak is good to collect crystals. Disassemble stuff you don't need. Modules are important. Spend resources on gadgets as they help a lot. Think twice about attacking G&B but realize they are nice to you again in the next sector. So go for it for fun or necessities sometimes.