Can I reassign certain keys

Please note the irony of the fact that I came here to ask a question and can't type in my question mark!

I bought a new MacBook this summer, and about a month after I got it, I spilt an entire cup of juice on it. Thanks to my fast flipping-over and power-removal skills, and hours of prying off keys and cleaning them individually, I managed to get away nearly scot-free. Unfortunately, I lost the function of my 'six', 'slash and question mark', and 'plus and equal' buttons.

Before we continue - yes, I know I am an idiot to have given my $1200 purchase a gentle juice bath. Yes, I know that I should be happy I haven't lost my whole computer. Yes, I should rot in Apple hell.

My poorly punctuated question is, is there any way to assign the 'six' to a different button on my keyboard.

Thanks for your time!