Haha... my title has alliteration. :p What happens when i draw parasite paracide and my monster slots are full? do i wait till i have an open space and then immediately play it? Do i take 1000 and not summon it? i dont know and brother just built an insect deck with 3 of them.

That is a good question, I would rule that since it cannot be special summoned it would stay in your hand as if it were any other card. I can't find any official ruling on it though.

Normally, when a monster must be summoned to the field by some effect and there are no available slots, the monster will be destroyed and sent to the graveyard.

Based on the wording, I'd say that the the 1000 lp damage is taken when the card is drawn and the summoning occurs at the same time. So even if there are no available slots I'd still say that the player would take 1000.