wow, you sound like me in a lot of ways. the "woe" for example! and the timid. about nothing feels more stressful than making a major purchase when it's so important and expensive.
make an appointment to get your old car tuned and maybe it will then pass and be driveable - then you don't have a deadline anymore and can shop for another car if that's what you want.
ask everybody you know (like your brother) to help you.
ask here*! people are very kind.
* I guess you did already
