Don't take it to a gunsmith, you'll just waste your money. The "trick" to re-assembling a Ruger .22 pistol is to return it to the same state as [b][i]before[/i][/b] takedown.
Before the mainspring assembly can be removed, the hammer has to be down, i.e. in the fired position. After the mainspring assembly has been removed, the bolt is next removed from the receiver. As the bolt is removed, the hammer is drawn back into the cocked position.
When re-assembling, install the bolt. Now, here's where it's good to pay attention. [b]Return the hammer to the down or fired position. Since there is no spring tension on the hammer at this point, hold the trigger back and point the pistol down until the hammer is observed dropping. Once the hammer has been verified to have been placed into the fired position, re-install the mainspring assembly. When re-installing the mainspring assembly, make note of the recessed area in the top of the assembly. The hammer stirrup (the little dangly thing at the base of the hammer) needs to go here. As the mainspring assembly is inserted into the receiver, ensure that the hammer stirrup is guided into the recessed area.[/b] Complete inserting the mainspring assembly and call it done. No need to wring your hands or leave your pistol laid up at a "gunsmith's" place of business.
As to not being able to disassemble right now, exactly what seems to be the problem? Sometimes the takedown lever can be overly stiff when re-assembled incorrectly. If that's the case, use the tip suggested in the owner's manual and modify a paperclip to draw out the takedown lever.