Keep in mind that marriage is no longer forever. Divorce rates are high enough between people from the same culture let alone those from different cultures. The good news is that there are alternatives to residency besides marriage.
Differences in culture can also wreck havoc on cross-cultural partnerships. There's a reason why I wrote think carefully before marrying a Peruvian and that's it's one of the top 5 posts on my blog.
One tip to remember is that speaking Spanish will help you greatly. You'll be treated differently than if you speak English all the time, it'll help you assimilate to the culture, and you'll be able to communicate easier. If you're looking to learn Spanish, check out Fluenz Spanish, Rosetta Stone, and Synergy Spanish.
Upping sticks and moving anywhere is complicated. It can get harder if you don't speak the language or if you don't have a job waiting for you. More often that not people end up begrudgingly teaching English. While there are other options than teaching English in Peru, they do take time to set up.
While there are plenty of people that do end up living in Peru forever, just remember to keep your options open. Don't limit yourself to one country. Take things in stride and realise that there are many things beyond your control.
The Ultimate Peru List recommends: