Hi
It is quite easy to do that provided you have room on the transom to remove the bar as sometimes it requires to be fitted prior to securing the engine down onto the boat transom.
If you do manage it there's a neat little idea of a "steering saver" which replaces the holding nut with one that has a grease nipple to maintain it. Only around £30 on eBay etc. I always fit these now but before that I drill out the tube using an adapted (extended) drill then grease it all up with marine graded grease prior to fitting
One thing to consider though, chances are if it's stiff it's not been maintained for a while so expect the cable to be worn, damaged or sheer a bolt etc. Prepare for the worst and hope for the best!
Let us know how you get on
P.s I've a decent hydraulic steering system available if you fancy an upgrade. Complete with all pipes etc. Used but very good condition. Cost over £700 new. I'd take £250
Peter @ Boatsandoutboards4sale ~
askboatsandoutboards4sale@sky.com ~ 07930 421007