If you wind up buying a valve spring compressor tool, be sure you're able to return it. I got one from Amazon and it didn't work at all. It was just not set up for the head. It was a C-type with toggle leverage, but it couldn't span far enough to be able to even start moving the lever. It got returned in short order.
The rental approach is the way to go. Get the biggest and baddest one that they have. You'll have to put a deposit down, but that's 100% refundable when you return it within the prescribed time. O'Reilly is 48 hours IIRC.
