definitely get new boots. it is not worth it, to have bad fitting ones.
when i bought my boots for Kilimanjaro, they fit comfortable right there in the store, like i was wearing tennis shoes. I tried on just 4 pairs, 2 different sizes and 2 types.
they are still just as comfortable. i have now used these for Aconcagua and Everest (low elevations) too.
I bought Zamberlan, but you should buy whatever fits your foot.