CARGirlVroomVroom503

So I recently bought a 1997 Chevy Trailblazer from my boyfriends Coworker. it had been sitting for 2 months so had to get a jump to start her up right out the gate (I've had no issues with the battery or alternator other then that initial jump to get her started). Everything seemed fine driving wise.. Still having some issues with figuring out whats wrong with the steering wheel and why its not autocorrecting its self back to the center when i turn either left or right, it'll just stay in the direction i turned it until i turn it back (but thats another issue for later). Well i noticed when driving home from work it started to backfire when i would accelerate from a complete stop. Well when getting on the freeway i started to accelerate and it then started to backfire repeatedly nonstop until i took my foot of the gas pedal. Everytime I would attempt to accelerate it would start to do it again and would feel like it was trying to die. So i got off the freeway and it started to drive normalishh but would back fire here and there until i got home. I let it sit over night, and the next morning i went to have a reading done and it came back with Misfiring. of course thats all the guy told me and wouldnt give me the codes or tell me if their were multiple misfires but just said its misfiring. I was called into work so i had asked my boyfriend to pick up all needed essentials for changing the spark plugs and that my dad would tell him what all he needed to get. Well he also decided to surprise me and went to change the spark plugs himself, well now it wont start. He also told me he was only able to replace 5 out of 8 spark plugs cuz he wasnt able to get to 3 of them due to a weird angle or something. Well I asked him did he get the ignition coils as well and he looked at me as if I was speaking french or something. So i then asked well you made sure to gap them correctly when replacing them, and then he made that same face so I'll assume no cuz he didnt even know what gapping the spark plugs meant.

At least he tried so I'll give him that...

My question is, What do I need to do to get my trailblazer up and running properly and what do I need to get to do that? What happened to cause it to not start, and what was making it backfire like crazy? Is there anything else that you think would be an issue I need to address also?

I really need this car to be working well and ASAP I start school for my apprenticeship for welding in a few weeks and will need it to haul my gear back and forth and to get to the job sites.