Given that Bintel sell Meade OAG for $109
https://www.bintelshop.com.au/Product.aspx?ID=5443 it wouldn't be dear or difficult to try prime length guiding. If you could sell the Tasco could could probably come out almost even.
Full focal lenght guiding will show the ability of your guiding skills and your mount's capabilities; and consequentially be alot cheaper than a new OTA. For long exposures if you don't go OAG - then you'll need very rigid gear to guide well (to eliminate or at least minimise differential flexure). I spent over a grand on my mounting gear and same again on focusers that can be PC controlled.
If your intended targets are dim they will require long duration guiding. For this to be successful you need really, really sturdy amd rigid gear - throughout your entire imaging chain, and possibly a way to maintain precise focus as the night progresses and therefore cools and this changes your OTAs focus.