TPS at idle (foot off gas) should be .38v-.42v. If it is reading higher & idle is high, check for a dirty/binding throttle plate that is not closing all the way before adjusting the TPS - plate should be fully closed at idle, all air goes through the IAC bypass.
At WOT it should read above 4.2 volts.
As to scan tools, there are a number of OTC 2000s on ebay right now - just make certain you get the cable (GM 12 pin) and cartridge (through your year) for your car.
. Right price is $25-$35