You don't need an expensive bike to do a tour. However, unless you're good at bike mechanics, it may not wind up being cost-effective to use this particular bike. You'll need a new crankset, a new BB, a new front derailleur, and it'd be a good idea to get new chainrings and a new chain. That also means that if the cassette is worn down, it will be a good time to replace that as well.
I'd get an estimate for the upgrades, and compare it to a low-end hybrid or a used road bike that already has a triple.