The campgrounds inside RMNP are on a 6 month window, so yesterday/11.18.22 was the opening window for 05.18.23. The reservation system is based off the Eastern time zone, so 10amEST/8amMST is the time when the window opens for reservations.
As noted above, Moraine Park Campground will be closed all of 2023 and expected to reopen in time for the 2024 season, with significant improvements made to the CG.
Glacier Basin is the only other real choice for you for inside the park, and D loop is the only one that has sites for larger RVs. D-144 thru D-150 should be able to accommodate larger rigs.
H E R E - Glacier Basin is the campground photo website that gives you a view of the specific sites. I've stayed in D-145/146/148 multiple times with my 28ft trailer and dually tow vehicle. I've seen larger rigs in those sites in the past, a couple of big motor homes were able to get in. I wouldn't look at the other loops at all for a larger RV.
For outside the park on the Estes Park side there are:
KOA Estes Park - likely too tight to get in to a site there with a larger rig and the sites are close together.
Estes Park Campground at Mary's Lake - This is run by the Town of Estes Park Recreation and Parks Department and they have FHU, W/E, and no hookup sites available. The FHU sites would likely be able to accommodate you as they are all pull thru sites and I've seen a wide variety of rigs there, with toy haulers and large motor homes. The W/E sites would likely be a bit of a challenge though for larger than 28ft.
Elk Meadow Lodge and RV Resort and Spruce Lake RV Resort are owned by the same corporation and are practically across the street from each other. ElK Meadow has sites that will accommodate any size rig with mostly pull thrus and some back in sites. Spruce Lake is all back in sites and is a bit tighter than Elk Meadow.
Manor RV Park is next door to Spruce Lake but on a different street, access is a bit tricky getting in and around in the park and the sites are tighter together than Elk Meadow and Spruce Lake, but I've seen larger rigs there so there's that.
Forget about Paradise on the River RV Park, as it's usually completely booked from season to season by returnees and is more of a challenge to get in/out. Same for Estes Park Campground at East Portal, it's more for tent campers and popups, with only a few sites the could accommodate trailers up to maybe 22ft.
There's also Yogi Bear's Jellystone Park and Larimer County's Hermit Park on US36 out of town. I've not stayed in either of these but have looked at them, of the 2 Jellystone might be doable. Hermit Park is also more for tent campers and smaller rigs.
H E R E - RV Parks in Estes Park is the camgrounds.rvlife.com website with reviews on the parks mentioned. I've written several reviews (ThominColorado) there.
My go-to park is Glacier Basin simply because it has the best views. For D loop, it's one way counterclockwise, but the rangers will allow you to go in "backwards" for sites such as D-145 which has an awesome view of Longs Peak from a different perspective. I know that it's going to be a lot harder to get reservations in Glacier Basin in 2023 with Moraine Park being closed all season.
Check the prices for the various websites noted. It's not cheap. Elk Meadow, for example was $82/night last season with FHU including cable. Mary's Lake is the least expensive but it's going to be in the $45-$57 range depending on site. Spruce Lake will be comparable to Elk Meadow.
Also be aware of the timed entry policy for RMNP that will (likely) be in place again in 2023.
H E R E - RMNP Timed Entry is info on the timed entry policy. Though it's not in effect for the winter season, it's been in place for the past several summer seasons and I can't see the Park Service NOT using it again in the 2023 season, as it's been quite sucessful in limiting traffic in the park. IF you have a campground reservation INSIDE the park, you don't need a timed entry pass, but you will need to show your campground reservation to several checkpoint sites.
ETA: Forgot to mention the WEST side of Rocky. In Grand Lake there's Winding River RV Resort and Elk Creek Campground and RV Resort just outside of town. Both would be doable for larger rigs. Winding River has FHU sites in one area of their park and W/E elsewhere. Layout of the park is sort of odd, but it's a nice place. Both of them escaped damage from the East Troublesome fire of a couple seasons back, but there's a lot of fire damage in and around that area, as well as the west entrance to Rocky.
South of Grand Lake there's a goodly number of USFS campgrounds available.
H E R E - Arapaho USFS campgrounds is a website for the USFS CG in the area, under "Granby" as the town. Stillwater and Green Ridge in particular could be doable and they are on the water and have spectacular views from the CG. Stillwater has water/electric hookups.
ETA: JUST RE-READ YOUR ORIGINAL POST, GLACIER BASIN CLOSES EVERY SEASON RIGHT AFTER LABOR DAY, SO UNLESS YOU CAN BE THERE LATE AUGUST OR LABOR DAY WEEKEND, IT WON'T WORK FOR YOU. LABOR DAY IS SEPT 4, 2023 AND WILL CLOSE THAT WEEK, WON'T BE OPEN AFTER SEPT. 5TH
Good Luck with your visit!
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