I DONT WANT TO SCRAP THIS CAR! HELP ME.

I have a 98 eclipse rs (420a) motor that has been a real pain and im just looking for a close to possible answer as to what might be wrong with it. Car will crank over, start and then just die within seconds during idle. Before it would run fine/ I did experience an overheating issue that I ended up fixing (blown heater return line). I would have to say when it really gave up on me I was driving from work. About 20 minutes in I lost all power (but not like electrical fail more like a power fail) pulled it over and noticed a awkward smell coming from under the hood into my interior. So I let it sit in my driveway for a couple of days. Start it up and day after day I would notice the engine shutting down faster with every crank. Looking at the engine I noticed the headers had a small crack and also what looks like some oil build up along the headers flange. Im assuming it has to be an head gasket, loss in pressure causing the motor to just shut down. The strange thing is that there is no check engine lights or indicators that make me think that its a specific parts, which also makes it harder for me to narrow it down. I thought it was the starter and had that replaced. The motor is getting fuel cause I checked the fuel line and the only thing I didnt replace or check was the spark plugs but will bad plugs cause a motor to just shut off when it never has a problem starting up/ it just shuts down instantly, with no hesitation or stuttering like most cars do. I dont know, Im just trying to write down everything I can think of but maybe Ill post some photos to help.
The main issue im having is the motor shutting off/ the most noticeable problem ive seen was the slightly cracked header with the build up around the headers flange/ a strange smell from under the hood and no indication lights or stuttering when engine shuts off. (Instantly shut down). Also when the car does start and shut down, it doesnt crank back over until later or the next day.
If it does turn out that its the head gasket, what is needed to repair this problem/ also is it expensive to fix and could I fix it myself without any major tools.

Thanks