just bought DR hi beams, never changed strings b4, should i just do it on my own or pay a store to change them cuz i dont wanna mess anything up

You can do them. You may need to do a setup afterwards, in which if its not an expensive bass I recommend taking the time to do also, and learning how to do it.

It's not hard to do. Couple hints though, string the strings through the bridge, then measure the string to about 3-3.5 inches past the tuning peg it's going on. Bend it there 90 degrees, then cut it about half an inch past the bend. String it from there. Also, when winding the strings on, keep an even pressure on them, and make sure that each consecutive wrap goes UNDER previous one. The strings should have a bit of a downward angle past the nut. These are the things I wish I'd known the first time I tried to change strings. Good luck and have fun :) (oh yeah, remember to only do 1 string at a time, too)