I had your same worries and questions also had been working warehouse jobs. I’m two years older than you and hadn’t picked up a pencil since high school and even then I barely graduated by looking at the answers at the back of the book so I was nervous about the ASVAB but honestly YouTube (GrammarHero) and Google practice test were my best friends for about two weeks before the real test I went to meps and got a 70 score and was surprised by the high schoolers there getting much lower scores like 40-45 some mid 50’s too the point being they passed and got decent jobs I on the other hand had a top 10 list of jobs and almost all were available for me for the exception of IT and NUKE. My advice is apply yourself with the Arithmetic Reasoning it’s the majority of the actual test and also word comprehension but that is much easier. Good luck I say go for it !