Is it the clutch, the transmission, or none of the above?

2004 VW Golf with a standard transmission. It has recently been to the shop for its 80,000 mile check-up. They flushed the brake fluid, new battery, new air filter, and suggestion for 2 new tires. A few days after getting my car back I noticed it was frequently difficult to shift into third gear. It seemed as though there was something blocking it from fully shifting into place. I have since noticed a little harshness with second gear as well, but the other gears seem fine. There is no difficulty shifting out of any gear. The problem seems to be at its worst when my car is completely warmed up and I have been on the road for a good 30-45 minutes. The kicker is that I am preparing to move from Mid-west to West coast after the holidays and drive this car from here to there. The budget is tight, but I think it is more important that I make it to Cali safely. Any help you can offer is much appreciated.

First thing to do is make sure there is enough fluid in the clutch master cylinder. If it is low you have a leak.

Maybe it needs a clutch pedal adjustment because the clutch is not fully disengaging at those gears. After warm-up, the problem worsens because of thermal expansion of the clutch plates.