Timing belt OEM Subaru or OEM Volvo

when I got my '06 sti 3 years ago I replaced the original belt with roughly the same mileage on it and it looked to be in fine condition despite being 13 years old.

I've done many timing belts. The locking tool is a "nice to have" but certainly not required. You should be checking your cam sprocket alignment before turning the engine over, anyway, so just take your time and be careful and you'll avoid most issues.

I have a 2007 S60 and the timing belt was replaced by a non-specialist soon after I purchased it. The tension on the belt has to be just right, and the non-specialist mechanic way over-torqued it. Had I not noticed the issue and taken the car to a specialist, it could have pulled the engine apart.