Jim, 1 aftermarket starter $120 you install it yourself = $120. The problem is that you are not 100% sure there is an engine problem. Where do you start, replacing the flywheel or the mixing elbow? You are going to need a new starter anyways so why take a chance of ruining an OEM $500 unit? Define "tough start" a starter with a worn out bushing will crank slow and even fail to move as the armature may come into contact with the field. It may develop enough play to jump the gear ring and even jam perhaps causing the aforementioned breakage. They usually heat up when such a condition occurs. I agree the starter should have been inspected when the first symptoms of slow cranking may have developed as now we have a busted starter that can no be inspected and a possibly damaged gear ring. In order to determine where a possible fault may lie we need to establish a base line. Get a new starter, see if the engine cranks slow; if it is real slow definitely look for a fouled gear ring or other engine causes but if it cranks OK or just a tad slow just keep it under observation. It could be a fault that takes years to develop and depending on how long it takes to damage the starter it may even be cost effective not to repair it at all.
I did too.
But...
With the new starter, if it is tough to start again, don't do what I did..
(2 starters) x $500/starter = $1000
Plus labor and the engine fix.
Jim...