Would it be possible to keep up or would i be overwhelmed by a hopeless struggle trying to grasp the new material while at the same time looking back at as well as relearning a few core concepts from single variable calculus? I have rather horrible basic knowledge from single variable, but I do know my way around linear algebra.
The reason for asking is a choice i have between "retaking" single variable this quarter but it collides with the schedule for multivariable calculus. Multivariable is probably much more important for later courses (electromagnetism and field theory) as well as just seem to be a lot more fun and intersting math.
The phrase "multivariable calculus" might be somewhat misleading. This might imply that it is different from single variable calculus, i.e. first you learned SVC, now you can leave that behind and you'll learn MVC. This is not the case. A great example of this is integrating with respect to two variables. Integrating with respect to two variables is a relatively simple and important concept in MVC, but does not rely on some brand new ideas developed only for this field of mathematics that introduce a completely different way of thinking. Integrating with respect to two variables is just integrating with respect to one variable twice. Unsurprisingly, this is no easier than integrating only once.
This brings me to my main point. In MVC, single variable concepts and their applications do not just only up occasionally, they are important in every chapter and every class. They laid the groundwork for all future concepts, and most problems in MVC are solved by reducing them to SVC problems.
In conclusion: As was already mentioned in some of the comments, I don't want to give specific advice for your situation. A friend or teacher who understands you better will be in a better position to give you specific advice. However, I did want to make you aware of exactly what a MVC course is and what will be required of you in terms of single variable knowledge.