Personally I would have it fixed. Or better yet, take the opportunity to get a little MIG welder and learn- it's not hard at all to learn how to do the welding necessary for sheet metal work! Don't be intimidated. This isn't a structural repair- nobody's life depends on it. And if your welds look crappy, you're going to grind them down anyway.
I think you should repair it because If you hit it with a wire wheel/angle grinder, I think you're going to find that the rust turns to dust and you're going to have holes. That rust is pretty bad.
I would recommend patching the bad spots rather than getting a new gutter. The Cool Cruisers full gutter comes in pieces without any of the rivet holes drilled. So it'll require some careful fit-up work (bolting the pieces down to the hard top sides and door headers, placing the fiberglass top on it to make sure it's all aligned, adjusting, tack welding, and then carefully drilling the many holes for the rivets. Fiddly work. If you take it to a pro, they're going to need the entire cruiser to do this properly, and frankly I wouldn't trust a shop to have the necessary patience. If you can bend the damaged sections back to flat (I'm sure you can), then I'd just patch the rusty sections. It looks like it's just the horse shoe sections that need replacing.
An in-between solution would be to just replace the "horse shoe" section with the cool cruiser panels if those are your only bad spots:
I would first bend the bent sections flat, brace it by tack welding some angle iron across the corners to keep things from moving on you, carefully cut out the corners, and fit/weld in the new horse shoe pieces. Then you just have to drill a few holes for rivets.
One of the things I learned with my resto is that sometimes it's easier to just patch the rusty spots than replacing the panel with aftermarket parts. Aftermarket parts always require a lot of fitment and adjustment because they're never perfect... and you have to spend a lot of time aligning the parts and measuring before welding in the replacement panels. Replacing entire panels for one section of rust can easily become a "throwing the baby out with the bath water" situation. Your rusty original panels fit your rig, so there's an advantage to keeping as much of the original panels as you can.
But seriously- get yourself a MIG welder and watch some youtube tutorials. You'll soon realize that basic MIG welding isn't a dark art and that you were intimidated for no reason. It's really not hard.