No no no no.
Lean condition on the lambda sensor indicates the mixture can't be corrected.
Lean mixture is either not enough fuel or too much air. Both of which the ECU will attempt to correct.
As you can smell fuel and its using a lot, I'd go with the latter.
Sounds very much to me like un-metered air on the intake somewhere so the fuel is being massively overcompensated.
To diagnose properly(!) and not just blame the sensor, check the spark plugs for fouling and the intake for leaks (spray brake cleaner or similar around gaskets and joints - if it revs up, the leak is sucking in the flammable substance).
On the 1.7s pay particular attention to the PCV pipes (97MF-6C342-AA) under the upper inlet. This pic is a bit misleading as the two upper bits run parallel to the cams but this is the pipe in question - http://fordcat.ru/shop/1/parts/1206596" onclick="window.open(this.href);return false;
May also indicate MAF although that would give you different codes and normally a poor idle.