Get the paper gaskets, not the turkey tray pan that most auto places will try to sell you-they suck. You can use some ARP bolts, Summit should have a kit for them. They are nice bolts, but a stocker bolt kit will do the job.
For the HEI, try a search on Google, or here on ***boat, its not hard, but easy to screw up. You should be able to find some detailed instructions. You will need new plug wires too, your current ones probably wont work with the HEI terminals. Existing plugs should be okay, but why not change them since you are changing everything else? You will need a timing light too.
For the intake, get some 3m weatherstripping sealant and use is SPARINGLY around the water ports, that will help make sure they dont leak. Be careful though-that stuff gives new meaning to the word MESSY.