It sounds like you need new hoods and new tape and new cables and housing. The actual pure replacement of the hoods will probably not need all of that but it sounds like the bike could use the love up there but also find out if your bars are corroded or not and new cables and housing will help things run smoother and work better. You really just need to remove the shift cables and you should be able to get them off but I would do all the work.

I am unsure what the river is but your local shop should be able to help order you some or one of the actual websites for the people who make the stuff could get you some or if you don't want to do all the work your local shop can take care of everything quite easily.