OP: go right ahead, you're not going to take no for an answer anyway, but don't get clever and try to improvise pressing in the headset cups, installing the bottom bracket or tightening your locking. Use your lbs for those. Out side the locking, the tools are somewhat specialized and essential.
I used to just use the LBS to press the cups in, but you might have luck having them install the whole for/headset/stem if you're not up for trimming steerers.