You might want to clamp it down in some way if you glue it yourself. Clamps can be pretty cheap or expensive, depending upon what you need or buy. For my money, a couple of strong ceramic or rare earth magnets would serve your purposes.
I'm afraid I don't know about cost. Maybe someone in the luthier section could advise?
If you do try DIY (personally I wouldn't if it were my best uke), then you'll need to clean off all old glue residue and make sure the surfaces are clean, dry and flat. Probably the best glue would be regular Titebond (but NOT their "liquid hide glue" - I've had problems with that stuff).
Magnets are a neat idea, but I think you'd want a couple of really firm clamps. Possibly tighter than magnets would deliver?
If it were me I'd be enquiring about pro repairs, just as you are.