H E R E - Estes Park is a previous post that may have some useful information for you.
In a nutshell:
Trail Ridge Road is scheduled to open Memorial Day weekend. They shoot for that every year. Some years it works out, others not so much. A couple of seasons back they got it plowed through and open, but couldn't keep it open due to late season storms dumping a foot+ up there.
The good news about Estes Park is they have a lot of shuttles around town and they are free. There's shuttles from the various CG inside the park, as well as some of the commercial RV parks. And shuttles can take you up to Bear Lake, but there is a very good chance it will still be frozen over and snow on the trail around the lake. Other lake trails in the area that high up will also likely still be snowed in, or will be extremely muddy. Lower elevation trails should be a better opportunity, if you're into hiking.
The bad news about Estes Park is your chances of finding a place to stay will be slim to none. The CGs inside the park are likely completely booked. There is an off chance of finding something in a commercial park; check the parks noted in my link on RVParkreviews.com. I would start with Estes Park Campground at Mary's Lake if you're going to consider commercial. They have FHU as well as W/E and no hookup sites, so you might be able to luck out.
Those shuttles mentioned previously? You'll need them, because I can assure you, there won't be much at all in the way of parking for a Class C in the downtown area. All of the parking lots fill up early, and stay full until late evening. There's parking at the visitor's center and the fairgrounds, but even those can fill up, particularly if there's any sort of event going on in town...and there usually is SOMETHING going on all the time downtown.
I can't offer you any feedback on the Green Jeep tours, since I've never done one. I can tell you that, over the past several seasons (I go up every year and have done so for close to 40 years) there seems to have been an increase in the number of tour vehicles seen up on Trail Ridge.
I know this all sounds like I'm down on Estes Park. I'm not. I love it up there; if I didn't I wouldn't keep going back year after year. I got my reservations back in December and January, as I have 3 trips planned up there. And there are wonderful places to stay, as well as visit, but timing can be everything. And I don't believe in sugar coating it. This is the reality of a resort town next to a national park that saw ~4.5 million visitors last couple of years. Other people must agree, otherwise it would not be so popular and so packed.