Collected Thoughts

Hmm. I watched most of The Sentinel, except for the last season.
You really don't need to, to enjoy the slash. Only a few key episodes are referenced regularly in the stories, and they pop up so often you would be able to write an indepth treatise on every aspect of them just from reading the fic.

The characters hardly evolve, the plots are very, very stupid, and the few good episodes seem mediocre compared to the re-tellings you're bound to read. Also the atmosphere of the show and the vast majority of the fics is completely different, so you can't really get "the feel" for the Sentinel universe from watching the show.

But! There are lots of explotions, handsome Richard Burgi and oh yeah, Garrett Maggart (sp?) is there too. ^_~

Due South I think it's necessary to watch the show to truly enjoy the fic. It's clever and funny, well-written and acted, the characters have great depths and evolve over the series, and most fan fic writers haven't felt the need to re-invent/re-tell the key episodes. So while I'm sure you already know the basic plot of, say, Victoria's Secret, now, important nuances are probably lost to you.
(Unless that's one of the eps you've seen, of course.)