Hey mondomantra, Check out Resources tab (https://www.speedrun.com/hl1/resources) for HL packages commonly used for speedrunning (2005 or Goldsrc ones). Also search for some tutorials on YouTube made by the community (especially d0t, qckdth, alexh0we and Tryedz). You can use 'crossfire' map for practicing bhops and c1a1c map for practicing object boosts. My advice is to learn the route (by watching runs or tutorials) and just finish the game, without trying the most advanced strats and no matter what time it is going to be. The game itself is full of tricky moments which you can improve on. With time, your PB will get lower gradually. Check out SourceRuns Discord server (https://discord.gg/sourceruns), feel free to ask there for more help. Good luck!

Current newest Steam version has a bunnyhop cap, which resets your speed from 544ups to 320ish while landing (Valve's attempt to nerf bhop). Steam version has other interesting exclusive features (like quickgauss) and you still can move fast with duckrolling technique, but bhopcap just ruins the experience to most runners.

You can only be banned for using scripts or external programs if you connect to multiplayer server because VAC is working there, so DON'T do it when BXT or other scripts are on. Otherwise, if you just run the game offline and comply with the rules of your category, you'll be fine.