As has been stated, the utilization aspect of your score has no memory so as soon as you pay the balance down and your card(s) report your score will rebound to the appropriate level. A far more important credit concern is that you don't have any late/missed payments, which certainly might be more likely to occur if you're maxed out and having trouble.
Instead, my main advice/questions to consider aren't directly credit related. You stated that the car's been at the dealership for a few months, implying that you haven't used it for a few months and have somehow been making due without it. My advice would be to put off the repairs indefinitely and keep doing what you've been doing. Do you have somewhere you can just park it indefinitely? Arranging the cost of a tow to that location would be much less expensive and possibly free depending on your situation (maybe a friend or relative who can tow it for you? AAA membership or something?) If you don't have somewhere you can park it indefinitely, you might also consider temporarily storing it. I've actualy done this exact thing. I used a self storage facility that also had parking facilities. It was completely secure and cost me around $65 a month. Of course this isn't the best option and if you can just take it home and park it somewhere, or find a friend/family member who will let you leave it on their property that's much better. Alternatively, you could of course sell it/scrap it and be done with it altogether.
Bottom line: It sounds like you've been making do without the car and you don't really have the money to pay for repairs - so don't.
Best of luck with whatever you decide though!
