I am taking a trip there the first week of August from Texas. I am a bass fishing guy but have never tried fly fishing. Should I get a day guide? Seems like learning the ropes with a guide might be a good idea. What attractions in the park are a must see?

Thanks!

are you talking about sights in the town of Estes Park, or in Rocky Mountain National Park?

Rocky Mountain. Sorry I'm a newb.

The one must-see in the park is to take a drive up and over Trail Ridge Road.  Along the way there are many excellent panoramic views (Many Parks Curve, Rainbow Curve, Forest Canyon Overlook . . .)


Up Trail Ridge Road, a walk on the tundra (parking/bathrooms just past the "Rock Cut") is usually excellent and brisk.





A stroll around Bear Lake is easy and works for a wide range of people.





A sleeper destination is to check out the Colorado River headwaters in the park (or just hike to the river where it's still trivially wadable).





For fly fishing –– I don't do it –– but the Big Thompson has quite a reputation, as you likely know. http://www.flyfishingconnection.com/cobigthompson.html
 

Fly fishing in the National Park itself is challenging.  If you have no previous experience, then you'll want a guide.  You can consider a fly fishing trip on the Big Thompson either in or out of the park, the section outside is probably better fishing.