I don't believe this style is meant to be serviceable in regards to hose replacement. If your hose is shot and needs replacement, you have nothing to lose by slowly and carefully trying to open up the plastic casing. Id have the hose fully retracted when doing so as the spring would be under the least amount of tension at this point.
If it doesn't work out, well, you needed a new hose reel anyway.
The Harbor Freight 50ft reels ones are a pretty solid bet for the money. I have two of them in service for 8yrs thus far without issue. I pulled off the junk hose right away and replaced it with flexzilla. Not the best quality like a COX or ReelCraft, but dirt cheap with the 20% off coupons.
