My wife and I faced a similar issue with our 13' Burro
. We decided to make our dinette/bed into a full time bed. We did not alter our front bunk because we have 3 year old twins... We decided to to this because our habit is to only go camping when it's nice and to be outside as much as possible while camping....we really only sleep and do a little cooking in the trailer.
We removed the cushions and set the table into the bed position. We measured and looked around for a matress. We found one that fit for $99 at Wal-Mart. It's worked perfect for us.
As for resale value...Who know how your alterations might effect the value. It depends on how nice/professionaly done they are. Personally I wouldn't put too much worry into this aspect since you said you intend on owning it for quite awhile. I say make it your own....customize the heck out of it to meet your needs.
I also empathize about the towing/backing situation. From experience I can tell you the only way to learn these skills is by doing them.