at 1k points you should keep your upgrades at minimum
also, try to have many lowcost units vs few high priced
as for the list changing question:
haemy,liquifier/venom blade
2grots/liquifier+aberration/venom blade raider
3 blasterborn venom/cannon
2x10 warriors/cannon/raider
5 wracks/liquifier venom/cannon
6 reavers/2 heat lances
there you have one extra warrior unit and a mobile lance in the raider vs the sniper squad