I have a 3PH log splitter from Harbor Freight. They quit selling this splitter for unknown reasons, but I think it was because so many people used their 20% off coupon to buy them. They sold for $500 and the coupon reduced that down to $400. I have just finished using mine to split wood and it works great, but you naturally have to tie up your tractor to use it. I'm thinking that your FEL quick connects won't be the 1/2" quick connects that most remotes are. I've found on my tractor that I need the tractor's engine running at 2000 rpm or more to ensure maximum flow. My tractor's pump puts out 9.8 gpm. Also, you will need to use the FEL's lift circuit and the raise position of the joystick. If you get into float, you won't have fluid to your splitter. In the curl circuit, you have to stay away from the regenerative position also.
I like my 3PH splitter fine. I use the 3PH to raise the splitter up and sit it halfway onto the back lip of my trailer. Then, as logs split and fall off, the trailer catches them. I can do a 2nd split or toss the wood into the front section of the trailer for transport. Without something to catch split logs, I find that picking logs up off the ground is tedious and sometimes they fall off the splitter and onto my feet if I'm not careful. Really, mounting the splitter inside a small trailer with long hoses to attach to the tractor is a better setup than the 3PH in my opinion. I've been keeping my eyes on craigslist for good deal on a small trailer. If your back is better than mine, then picking up rounds and splits off the ground may not be an issue.
I would think a 3PH splitter in good shape would be worth $250 to $300. I'd offer $200 and then dicker a bit on prices. Having to buy new hoses and quick connects is something extra you will have to consider and that will be over $100 by the time you get set up.