Do the gears crunch, indicating a clutch problem (ie: does it feel as if the clutch is not engaging at all?), or are the gears hard to "find" as if the lever/cables/linkage are not lining up properly? If the latter, it could be the nylon "bush" housing at the bottom of the gear lever, they can crack (but can be replaced), or the nuts/bolts can be loose, leading to a very vague gear change and difficulty selecting gears. Also the rubber bushes at the gearbox end of the cables can wear out leading to similar gear selection problems, these can be replaced.
1996 Portofino 20vt & 2000 Pearl White Plus
1985½ & 2016 2017 Fiat 124 Spider + XF Sportbrake