Most likely worn components in the gearbox, which would almost certainly require gearbox removal and at least partial gearbox dismantling. I would suggest getting quotes for the work to be done and quotes for a reconditioned replacement. Sometimes it's cheaper to put in a recon than have the repair done. The yellow pages should list gearbox specialists in your area.
I heard once on the program "deals on wheels" that some fiats clutch pedals bend over time causing gear change problems, maybe worth having that checked out first as a new gearbox on one of those will probably be costly.