I have Nova's and 500's...
...as well as 590's, a Win 1300 and a Beretta 1201FP.
I don't own an 870 but my shooting partner has a couple...fine shotguns.
The 500 disassembly takes some practice, but not hard to master. I find that most outings doesn't require that level of diligence in cleaning.
About 1/2 my 500's needed a 200rd Break-in to get a decent action...the other 1/2 were fine out of the box.
My 500's typically don't care for the cheap WalMart Winchester shot...they do fine with the black-box Winchester, just about any Federal, Remington...Estate shot use has been with mixed results.
I'm short with short arms so I've used the Hogue short stock and added a Limbsaver pad...gets me to 13" LOP and a very pleasant shooting experience from 7.5 shot to the Brenneke "Grizzly Tamer" slugs.
I've got some with SF forends, others with the Hogue Forend (I like the feel). Most have some sort of Side-Saddle for on-gun access to fresh ammo'.
My Mossy's run, so do all the others including my Nova's which I very much enjoy. I like the sights better on the Nova (especially for 100yd slug shots)...the stock is long but the overlapping forend lets me pump 'em just fine with a more aggressive stance. The Nova's typically pattern better with Buck' which is no huge surprise given the difference in barrels.
With a good break-in and some practice your 500 should perform just fine for your class experience. Make sure you find out what it likes for ammo'...try to put at least 200 shells through it ahead of the class (of various types) and think about respecting it for what it is...a decent pump at a good price which has served many quite well.
In the end, your findings will be your findings...if the 500 doesn't work out for you...should be able to recoup enough to get you into something else. I've found that most go-bang implements are like shoes...need to fit the user/operator.
Safe Shooting,
CZ52'
p.s. 870 (although a fine weapon) 10 times the gun indeed...then my 3-shot drill on steel with an 870 should be .12ish with the 870...yeah, right