i assume you have some kind of music bar for the 6-1/2 speakers. factory Dash speakers are 4x6 not 6-1/2". even if you can put them in dash why would you want to the dash would be covering most of it.
granted i know a 6-1/2 is better than a 4x6 but no need to try to force someting if it's not goin to work to it's full ability.
now a option i did in my 95 is added a set of 6-1/2" speakers in my doors (custom installed) and used quick disconnects for when i want to remove the door.
2) Is there anything else that I will need to do? I got a cheap 30 dollar HU a few weeks ago from Pyle Plus and it sounds ok. Couldn't afford a better one but the factory HU bit the dust.
what are you trying to do? get better sound? make it louder, both?
old saying is cheap stuff isn't good and good stuff isn't cheap.
your not goin to be any louder just replacing speakers.. may seem that way but radio puts out same power no matter what the speakers are rated at. thats how alot of people get suckered into buying stuff they just see big numbers, most of which are crap anyway since it's peak/max power, RMS is the true power rating
give you a idea of my system, keep im mind i work for a car audio company, i didn't go high end i went for "bang for buck" on alot of this since it's in a jeep and subject to bein damaged (IE: weather w/ top off, off roadin etc)
Memphis MC462 (4x6") ~ $120
Memphis MC62 (6-1/2") ~ $120 - custom installed
JL Audio TR400cx (4") - ~$100 -i had these from a old system
JL Audio 12w3 YJ stealth box (~$1200, way 2 much money, thank god i work for a audio shop) - no longer made
Memphis MC3004 (~$450)- 4 channel amp - 75w rms/channel - Had from old system
i have my dash & Door speakers off 2 channels of the amp, crossed over about 100hrtz, and the other 2 channels Bridged on the sub, my music bar is run off radio since right above my head, i have a inline cap on them (x-over)
i have had system for 6+ years and still love it. can have top off and goin down freeway still hear everything crisp & Clear, nice thing is you can do systems like this in steps.
couple other things dont waste money on stuff just to get it. better to go with out a little longer to get a better set of speakers, than get something bc it's cheap just to replace it again. when you get some more cash i would upgrade radio as well