Tristnal has pretty much hit the nail on the head here. If you're seriously looking for a raiding guild, you should probably optimize your character first.
First, yes you are way above the expertise cap. Get Hit/Expertise to 7.5%. Once you hit that cap, as a Ret Paladin, you should be reforging Haste. To clarify, your stat priorities are Hit/Exp(7.5%) > Haste > Mastery > Crit. For gemming, on Red sockets gem 80 Str 160 Haste, Yellow sockets gem 320 Haste, Blue sockets gem 160 Haste 160 Hit.
About professions, yes Mining is maxed out, but outside of tanking it offers no bonus in a raiding environment. Now semi-hardcore - hardcore guilds would ask you to change it, however if you're just looking for a casual raiding guild it should be fine. In the future though if you're looking at serious raiding you would want to drop Mining for another Profession.
Bonuses from professions include:
Blacksmithing - Socket Bracers/Gloves, adds 2 prismatic slots. For you means 640 extra haste.
Jewelcrafting - Gives better gems, meaning 2 x 320 strength gems for an extra 320 strength all together.
Alchemy - Increases duration of flasks by an hour and gives an extra 320 strength from a flask.
Inscription - Gives a better shoulder enchant, granting 320 extra strength.
Enchanting - Allows you to enchant 160 strength to your rings, for a total of 320 extra strength.
Leatherworking - Gives a 500 strength enchant to bracers, an overall 320 extra strength.
Engineering - Synapse strings gives 1920 strength for 10 seconds every minute along with speed boosts and good utility.
Herbalism - Only good for prot/ret, would normally not recommend. Gives 2880 Haste for 20 seconds via Lifeblood. 2 Minute cooldown.
Tailoring - Back enchant gives 4000 attack power for 15 seconds. Not sure of the CD on it though.
These are just outlines of what professions can give you, and if you're serious about raiding these bonuses will help much more than Mining.
Again this is just meant to be informative and help you a little more in raiding overall. About guilds, I could care less, however if I were you, make sure you have logs that measure performance when searching for a guild. Many require these to make sure that damage/healing meets expectations.
Good luck in your search!
EDIT: Derp, forgot Tailoring and Herbalism.
Edited by Craved on 4/11/2013 7:28 AM PDT