Good luck.

I, too, am bad at cleaning. And I end up with a lot of stuff that I don't need, so I guess I'm a hoarder too. Here's what works for me.

For cleaning - Small steps. Do something that only takes a minute - unclutter one table or a half a table. Unload half a dishwasher.
Hire someone if you can afford it. Just enough to take the edge off of the mess. And yes, I de-clutter before my person comes to clean. otherwise the cleaner will never finish. And if there's too much to de-c;utter, I just tell him/her to leave the cluttered room alone, and just clean what's not a difficult chore.
Invite someone over. I have to clean if I have guests.
I'm okay with a little bit of a mess. The trick for me is to never let it get really bad.

Re hoarding - here's what works for me - sort of. Some of my stuff is just trash - for that, i get a garbage bag and keep putting things into it until I get tired of the whole thing. Then I throw the bag out, and what is done is done, what is not done is not done, but it's better than nothing. Same thing for items that I'll never use but could donate. Get a bag and load it up with donations until you're tired of the job. Then take it down to Good Will, and you're done. The trick with hoarding is that you never know what will come in handy later on. So at least get rid of some of the stuff you know you'll never use and don't spend a lot of time wondering. The idea is to get something positive done so you'll feel good. Anyway, that's what works for me - sort of.