I wouldn't worry at all about touring round Europe, though it might be a good idea to do a shorter tour or two in the UK first to get a feel for it.
Before a tour, I'd strip, check and adjust everything. Depending on how old they were (and erring on the conservative side) I might replace brake and gear cables, chain and freewheel/cassette. I'd put new decent quality tubes in, and fit a pair of tyres that didn't have much use on them - Marathons for sure, as puncture resistance is key for touring. And I'd do all that with enough time for a few long-ish rides before I left, to make sure everything is ok.
I'd take a decent set of tools with me to cope with most breakdowns - certainly a chain tool, freewheel/cassette tool, crank and bottom bracket tools, 6" wrench, allen keys, screwdrivers, spoke key... together with several spare tubes and a few spokes. With all that, the chances of not being able to at least limp to a bike shop or mechanic would be, I think, slim.
And for a worst-case scenario, I'd make sure I didn't have any more with me than would fit in a rucksack, and I could dump my bike (which cost me approx £250 to build excluding the Brooks saddle, so don't want to lose it but it wouldn't break the bank), buy a rucksack and come home by public transport (bringing my saddle with me).