I forgot to dismiss my follower before becoming a werewolf, and I can't seem to dismiss Aela to get my follower back that I had.

Will my previous follower still have all the gear I gave her to hold when I return to get her again?

Yes, assuming that nothing happens to them in the meantime. Aela will remain your follower until the end of that mission. There are also a few other missions later on in which one or more of the Companions will be automatically assigned as your follower.

yeah i forgot my follower would leave when i initiated a companion quest, I went to the blacksmith to sell my gear and Lydia was GONE. I was pissed for 10 seconds until I realized she might be @ breezehome, and sure enough, Farkas was waiting for me @ some ruin, and lydia had all my gear I gave her when I had her rejoin me after the quest.

scared me for a second though lol

yes they should have all of the gear.

you just have to figure out wheere they are.

dragonreach, breezehome, riften etc.

As far as I know, the Mage follower Illia is still bugged, so If she gets replaced by a temporary follower (like from a Companions' Quest), you can't get her back without console commands.
Followers that wait too long without being dismissed generally return to the location where they were recruited (or the appropriate hold house for housecarls).