A pleco is a great idea, and you don't need to get a run-of-the-mill H.plecostomus (they can grow up to 24" and are poop machines) - try a bristlenose, rubberlip, or another small plec. They tend to be more industrious cleaners and they contribute less to the nutrient issue (less poop=less phosphate). If you do get a 'standard' plec, get a small one. The larger they get, the more meat they want in their diet and the lazier they get. Believe it or not, a 2" baby will remove more algae than an 8" monster, and poops a LOT less
Regular water changes using a gravel vac will help lower nutrients as well by removing the poop and any leftover food before it breaks down.
If you can get some help to remove what's there now, a MagFloat magnet cleaner might help keep it at bay once the glass is clean. How about asking a friend or neighbor over and offering them a beer (or a case, if the problem is really bad
) to scrape the algae for you? Then once it's gone, use the MagFloat religiously, every day, and it should stay away. This is how I keep coralline from growing in my 90g - I miss bits here and there, and once it's established I need to use a razor blade (about once every two to three months, and only in a few spots), but swiping the glass daily is a huge help.