First of all I must say I have no personal experience about the 1.7/1.8L F-series, but from what I've heard from people there shouldn't be any major structural problems with the construction. Some ignition or carburation related quirks can be expected, but they're usually not caused by any engine internal fault.
A friend of mine has a 1990 R19 TXE with a 1721 cm³ fuel-injected and catted F that's done over 220k km and the engine runs fine, so signs of fatigue. If you have a choice, though, go for the latest 1794 cm³ / 110 bhp version with multipoint EFI, as the 1721 of the TXE feels slightly poor on torque.
I don't quite understand the bad reputation the timing belt has in the USA, in my opinion it is reliable AS LONG AS IT'S RENEWED AS RECOMMENDED. What shouldn't be overlooked is that even if the specified mileage hasn't been reached, the age of the belt is just as crucial; Let's assume the engine's done only 10k km in five years, the belt must still be renewed 'cause it's reached the five year limit and become potentially brittle with age.
Changing the belt can be done by a home mechanic, there's nothing mysterious about it. And even having it changed is a routine task nowadays for garages and shouldn't cost too much, after all it must be renewed relativly seldomly. It's very recommandable to renew the tensioning roller(s) and possibly water pump at the same time while you're at it.
These dry cylinder liner engines can be bored oversize and oversize pistons fitted. Of course the boring must be done by a competent machinist, in that sense of course the wet liner C is easier/cheaper for a home mechanic to rebuild without external help. I've heard rumours that there weren't oversized pistons available for some versions of the F and that a new block should be purchased, but I doubt if that is true. It's probably been some official Renault dealer claiming this in an effort to cash in on the customer...
As far as I understand, most of the 1.7/1.8 R19s have power-assisted steering. When inspecting a promising canditate, make sure there are no leaks in the system as they can be expensive to put right. If there's a leaking axle seal in the steering rack, you need a new rack, the sealing can't be replaced separately! A new rack costs from roughly 500 euros up...
