I've got the 150 myself and I know my cables are stretched a bit and need replacing, but the gears still engage properly, was your gear select returning to neutral properly after being in forward or reverse, if it wasn't returning to neutral properly thats a good sign of a stretched cable. best of luck with it mines got over 950hr and still going strong. bit like a car having done about 40,000 miles I reckon, plently of life left in the old girl with annual servicing.
As for the impellor I was told as long as the telltail is pumping strong then all is good left as, maybe quick inspection wouldn't hurt though.