Ernie,

No problem casting those size flies you mentioned, even some bigger depending upon their weight. It is good to read up on things, even more important to learn to cast properly, way more important as a first step. Check You Tube for beginner fly casting instruction. Texas is a big state so I can not give you any info on local fly clubs in your area. Texas forms the Texas Council of the International Federation of Fly Fishers. There are a number of fly clubs associated with this great organization. You can check out the Texas Council at http://texascouncilifff.com/
Check them out an look for local fly clubs. Most clubs will offer some form of casting instruction. Also, if you have any local fly shops, check with them.

Don't overthink it, just do it.

Larry ---sagefisher---