So I've recently bought an -04 LS 430 to replace my old -90 LS 400 as my daily driver.
It's been maintained fairly well but I noticed that it's been a while since the engine oil and filter were replaced, so I decided to do that for good measure.
I should point out that I'm not a mechanic or anything of the sort. I own and drive these cars because I love them, but they're very, very expensive in my country,
especially when it comes to dealership maintenance and repairs, so you either have to be extremely well off or you have to be willing to do maintenance and repairs yourself.

I've learned a bit over the years repairing the LS400, but I'm still an amateur. So with that in mind, I'll skip ahead and just detail what went wrong here:

When I removed the old filter, its o-ring decided to stay put. Since I'm a clumsy bastard, I failed to notice this when I screwed the new filter on. The new filter is a MAN filter (I used these for the LS400 too without issue), the old one's an original. These o-rings are slightly different in size, so the seal ended up being terrible of course.
Long story short, I had oil spewing absolutely everywhere. I took the filter out to see what the hell was going on, and then I noticed the o-rings. "Crap".
The mess isn't as bad as it sounds though. I turned the engine off immediately after I heard the leak, and as soon as the pressure dropped a bit it stopped gushing all over the place and just peacefully leaked out.
So after confirming what caused the mess, I started cleaning the car up. Now, the oil filter is directly underneath the serpentine belt on these things, so I got some engine oil on the belt. I checked carefully and found some spatter.
I mean, it's definitely not drenched or anything, but still... the thought of that belt slipping around in there makes me really nervous.

Replacing it is definitely not something I want to do since the belt's practically brand new., so my thinking was that I'll start it up tomorrow to see if it slips. If it doesn't slip, great! But if it does slip, I'll have to take the belt out and clean my mess up properly.
After pondering this idea for a while, I eventually realized that starting the engine up to see if the belt slips might not be a particularly great idea in the first place, which is why I'm here for some input from people who aren't as clueless as I am.
I'm also wondering what I should use on the belt and those rings that hold the belt to get the oil off without damaging the belt itself. I have a steam machine, would that work?

Thanks in advance, and sorry for being a bit all over the place in the post.

UPDATE:

Took the serpentine belt out and cleaned both the belt and the pulleys with engine degreaser. Wouldn't even have had to remove it, there was barely any oil on it at all. Eh, now it's clean. Car runs fine again.

 

Your post is too long to read....

 

Just for future reference, you can use Brakleen as an excellent cleaner on the belts. It leaves NO residue and with a good wipe down afterwards, you won't have any issues. Use the pressure nozzle on the can to also squirt and clean the grooves on the pulleys. Just don't soak the belt with the Brakleen.