I have 2 RES, both of which were in a 75 gallon, however they have since decided they don't want to live together (after I have had them together for 16 years), so they will come to school in separate tanks. Anyways, you should definitely get the Python, it works great and makes refilling the tank SO much easier. You can use it to empty to, although I don't because then I can justify not exercising that day, haha. If you can't find a home, or decide to keep the, getting the right filter will make life so much better.
For years I had the in the tank one, which kept the tank clean for only a couple of weeks. In February I bought an Aquaclear 110, which is a hang on the side tank, and it is wonderful. I only have to change the media in the filter and rinse it out once a month, and the water has been crystal clear since then. I have to add a few buckets a week of water due to evaporation, which isn't too hard. I also occasionally do partial water changes too, just so that I don't leave the same water in the tank for a long time. This however can be done at leisure, since its not because you have a stinky tank. Also, with the Python, it makes it a lot easier. The only real downside is because most turtle tanks are not filled all the way (mine is about 3/4 full with water) there is a splashing sound as the water falls. I have heard you can quiet it by adding hanging plastic plants to the outflow, but I have been to lazy to do that yet.
Even better are external canister filters, such as Eheim, and Filstar XP3. They work even better than my filter, and are quiet. They can be a bit expensive, but are well worth it as they keep tanks clean for months and months.
here's an article
http://www.austinsturtlepage.com/Articles/filtration.htm
There's also a turtle forum: turtleforum.com, that may be worth joining. You can ask all types of questions on equipment and care, and also can ask for advice on rehoming turtles.
Sorry for the long post. I know how much work turtles can be, but the right filter makes them so much easier.