New or second hand?

[Bluetree]

Try to buy a cheaper version of the same bike you will be riding. That way, the geometry will be the same and you have time to solve any sizing and fit issues.

I went to Hawaii and found a Specialized shop that rented road bikes. Their rental bike in my size (aluminum) had the same geometry as one of my carbon bike at home. Before I left, I wrote down all my measurements and packed my stem, saddle, pedals and shoes. When I got the rental bike, I borrowed their tools and was able to swap out everything important, including removing all the spacers. The difference in handlebars was negligible and the seatpost had the same setback (I called beforehand and asked).

When training for a long ride, even the smallest changes can lead to discomfort or worse. Preparing for it with the closest possible equipment will save you from a lot of potential problems.

(And I agree, the 52cm sounds a bit small for you. But if that is your only option, it's all the more important to solve your fit issues before you leave, such as needing a longer stem)