It's a very individual choice but if you're not sure what breed, or when, then just slow down. Think about the qualities in your old dog that you loved - were they really loyal and friendly, or were they a 'one human dog' or were the just an exercise nut you could always be out and about with? Are those qualities you want again, or do you want something different?
In the end, a new dog won't replace your old dog but you probably will compare them - because that's human nature, and that's okay. You just need to be able to accept that yourself and not expect too much to quickly from a puppy.
Puppies are crap. They're horrible, nasty, wee and poo producing sharks for about a month or two (depending on breed/breeder possibly longer) and then they're stroppy little bastards for another few months. Personally, I think anyone who says they love having a puppy is either insane or not putting in 100% effort - after eight weeks, when my bitch has a litter, I'm practically throwing them out the door.
I'm not trying to put you off at all! But I do often find that people who come to me having lost their dog have forgotten how bloody horrible puppies are - they remember their amazing, perfect, beautiful adult dog and they've forgotten about the turd-eating, wee producing, evil-eyed, land-shark they lived with for a year.
Rescues take time as well - more than the 'three months' people claim, I think.
BUT, if you think you're ready to deal with that again - do go for it. You already know how much dogs bring to a life. But if you're not, then that's okay - it's better to wait to you are sure, then regret it (both for you and the puppy).
I'm sorry for your loss though - it's horrible to lose them.