Your available time will dictate how far you can travel, and will go a long way toward determining the overall cost.
For planning purposes, I’d pick up a copy of Microsoft Streets & Trips. You can experiment with different routes to your destinations - interstate highways for covering distance, or backroads for entertainment. Paper maps from sources like AAA can alert you to scenic roads, which you can then plug into MSS&T.
If you’re serious about covering distance, on the interstate highways you can do 600 miles in a day. If you’re tough and determined, you can do 800, but that means keeping your stops very brief, and at some point this stops being a fun vacation. You can do 500 miles on back roads in a day if you aren’t stopping for touristy stuff. Don’t plan a whole bunch of max-distance days in a row; this will get to be a real drag in a hurry. I’ve ridden a motorcycle from Ann Arbor to Denver several times, and I typically break it into a 750 and a 550 mile day; once I hit Denver, I take my time traversing scenic twisty roads for fun.
Cost:
What kinda hotels do you like? Crusty hotels? Fine, 60/night. Hampton Inn, Holiday Inn Express? Double that. Lodging cost = /night times # of nights.
Camping? KOA’s can be nice, but not always - but they are always expensive. When I was a kid my parents had a national campground guide: no matter where we were, at around 6:00, Mom would whip out the book and find a satisfactory campground somewhere just up the road. This book, or something like it, is probably still available. If you’re not staying at a KOA, expect to pay $10-$20 a night. If you want to stay at a campground IN a popular national park, you’ll want to make a reservation far in advance. Note that a lot of nat’l parks have numerous private campgrounds and hotels just outside the park boundary, so don’t sweat if you can’t get a space inside the park.
Fuel? Figure 25 MPG. Fuel cost = $2.40/gal times # of miles divided-by 25 mpg. Shortcut: ~10 cents per mile.
Food? You’re going to be eating out pretty much every meal, except maybe continental breakfasts at hotels. Figure lunch + dinner times two people = $30/day.
National park entry fees vary. If you’re going to visit a lot of them, consider a seasonal all-parks pass of some sort, which may be cheaper.
That pretty much covers the basic costs. The rest is touristy stuff, like T-shirts and other souvenirs.
What to do/see:
As a kid, I made numerous trips out west with my family in a station wagon towing a pop-up camper. We did lots of camping and hiking in the mountains, so I enjoy that stuff a lot. As an adult, I ride a sport-touring motorcycle, so I really enjoy scenic, twisty roads, which happen to be mostly found in the same areas. But I also enjoy the change of scenery/landscape as you move across the country; watch for this as you go from farmland to ranchland to scrub to mountains to desert. A few favorite destinations, tours, and roadside attractions from recent memory:
-the Great Platte River Road Archway Monument near Kearney, Nebraska. Touristy on the outside, but the exhibits tell a neat history of the place.
-Pikes Peak, but only if you’re in good health; summit is at 14,000+ feet.
-Rocky Mountain National Park. If you’re going sometime other than June/July/August, check for road closures.
-Loveland Pass.
-Million-Dollar Highway from Ouray to Durango, Colorado.
UT128 into Moab.
Dead Horse Point state park.
Canyonlands (“Island in the sky” district).
UT95 from Blanding to Hanksville.
UT24/12 from Hanksville to Bryce Canyon.
Bryce Canyon nat’l park.
Zion nat’l park. (short, sweet hike: entering park from east on UT9, watch for parking lot just before tunnel entrance several miles into park. Trail goes up from north side of road to an incredible overlook. ~1 mile roundtrip, excellent vistas.)
Grand Canyon nat’l park. Short rim hikes on the south rim are easy, especially if you make use of the shuttle bus.
Hoover dam; look into the tour.
Yosemite nat’l park. Scenic approach is from Lee Vining, over Tioga Pass, into the valley. Fun/short hike is from valley floor up to Vernal falls and Nevada falls, but expect to get wet unless you’re going very late in the season.
Las Vegas strip. Gotta see it to believe it.
Been a long time since I was at Glacier, but I’d love to go back. Consider going there.
Salem Sue, a giant fiberglass cow in western North Dakota.
See www.nps.gov for national park pages; they’ll tell you what you need to know about all the national parks, including road maps, trail maps, safety warnings (that’s really important in some of these places) and lists of potential activities. Other stuff can be found on Wikipedia or elsewhere on the web.
See also www.roadsideamerica.com for amusing touristy roadside stuff along the way, e.g. the giant wooden squirrel in Longview, Washington.
As you do your planning, accept that you will not be able to do everything in one trip; this was hard for me when I was setting my my first road trip west as an adult. Don’t try to cram too much into one vacation, or you’ll be stressed the whole time. Give yourself plenty of time to do the things you do plan, and leave other stuff for future trips.