I think that other thread does cover it all, so I won't comment on that.
For finding gear upgrades, I highly recommend Lootrank.com. You can set many conditionals for the search, and it will provide you with an extensive list of gear options. I did this search for items you could obtain easily with a touch of Int, solid MP5 and good spellpower:
http://www.lootrank.com/wr.asp?Cla=64&A ... &k5=0&k6=0Ultimately, I don't think you need to be hesitant to do heroic 5 mans; Realize that some of them are considered harder than others: Halls of Lightning, Azjul-Nerub, Old Kingdom, and Occulus jump out at me as the hardest (based on my admittedly feeble memory). Some are quite straightforward- Utgarde Keep, Violet Citadel (although 1 or 2 bosses there require good communication), Nexus, Strath and Drak'Tharon. All of the latter should be doable with a decent selection of Blues, particularly if you have a good tank or solid DPS who can cover for your weakness.
Be honest when you go in a PUG- let them know you are working your way up in gear, but can handle it. You'll lose some groups that way, but you probably did not want to go with them in that case anyway. Good groupw will be able to adapt to your limits and get thru steadily, if not perfectly.
And remember, pushing yourself in these situations is great. You really learn how good a healer you can be when you are using every ability, cooldown, and strategy in order to get the job done.
Edit: And Auggie beat me

Great minds I guess...
2nd Edit: Auggie, I noticed you put mp5 over spellpower on Lootrank values; I didn't find mana pool to be as big a deal when I was starting heorics as pure thruput was. The fights tended to be short and high intensity. I'm curious as to whether others found mana pool or thruput the limiting factor.