I've seen a hundred different threads saying different ways to do it. The neck I am refinishing is a black neck off a cheap Magnum P-Bass I'm pimping out, out of boredom.

I was planning on stripping it with some type of thinner, sanding it with 800 then spraying on a sealer.

Would anyone advise for or against this? Or can they suggest a different way to go about it?
If you're actually refinishing the neck (as in putting a real finish back on the neck), then you're going roughly the right direction.

If it's a poly-something finish on there currently, you may find that it's tough getting the stuff off. You'll want to prevent your getting whatever it is you're using under the fretboard (else you'll find your fretboard lifting off), so you'll want to mask the poo out of it. You can try one of the Citristrip products; "thinners" will likely not work at all.

As for refinishing, you definitely want to put a real finish on the neck; I'd advise against any of the oil finishes if you plan on using the bass much. If it were me I'd go with a satin poly-something clearcoat. You'll have all the benefit of a satin-finish neck while still protecting the neck against dings, dirt and moisture in liquid form (sweat).
What dspellman says.

If the stripper doesn't work, I would use a scraper, followed by orbital sander, followed by hand sanding.

I think the choice of finish depends a bit on your skin chemistry and the inherent stability of the neck. Satin spray can poly is a good safe bet, and worked very well on a s/h Warmoth neck I bought. I have one that I finished by applying poly with a fad - cotton balls wrapped in lint-free cloth - about four very thin coats that you can barely distinguish from the unfinished wood. The idea is that it is enough to seal the wood against moisture and dirt, but will wear through to a "relic" bare timber finish fairly quickly. I'm happy with that because my 1934 Gibson has no finish left on the neck, but it is stable, and feels comfortable with all the years of grime and skin oil. - But I've got dry skin.
Thanks for the input guys, I'm not even bassist and this is more a cheap project than anything. I'll pick up some stripper and satin clearcoat for the neck. Just wanted to check using a stripper wouldn't somehow destroy the neck.